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مشاهدة النسخة كاملة : اسئلة اختبارات اسالة اختبار الانجليزي عام مصوره لعام 1436


khhshamari
2014- 12- 18, 08:56 PM
مرفق لكم الصور الي قدرت اصورها لمادة الانجليزي عام

fno
2014- 12- 18, 09:09 PM
تكفون نبي الحل

دفره تايم
2014- 12- 18, 09:13 PM
ابي الحل بليييز :39:

khhshamari
2014- 12- 18, 09:14 PM
1.C
2.B
3.A
4.d
5.A
8.c
9.c
10.b
11.d
12.goes
14.b
15.b
16.a
17.b
19.a
20.b
21.c
22.c
23.a
26.b
27.a
28.d
29.a
38.d
39.a
40.b
41.a
43.b
44.a
46.d
48.d
49.d
50.a

هذه الاجابات ان شاء الله صحيحة بنسبة 99%

أموون66
2014- 12- 18, 09:15 PM
نبي الحل بسرعه

دفره تايم
2014- 12- 18, 09:17 PM
الأجوبة ناقصة بس يعطيك العافية :36:

khhshamari
2014- 12- 18, 09:53 PM
الله يعافيكم
بالتوفيق للجميع

khhshamari
2014- 12- 18, 09:54 PM
الله يعافيكم
بالتوفيق للجميع

ابو ريما 1
2014- 12- 18, 10:05 PM
والله ان المراجعة زينه وشينه ..
بس ياليت تكملون الحل ويكون صحيح

نادر الجعفري
2014- 12- 18, 10:46 PM
طبعا بنقل لكم الحل لبعض
الاسئله .. لان تصوير الأخ يالله شفته
وناقص كثير ... واذا اكتملت الاسئله
ابشروووو...... والله اعلم
1-c
2-b
3-a
4-d
5-ماشفت السؤال
6-
7-
8-c
9-c
10-b
11-d
12-goes
13-
14-
15-
16-
17-
18-
19-a
20-b
21-c
22-c
23-a
>
>
>
26-b
27-a
28-d
29-b
>
>
>
>
38-d
39-a
40-b
41-a
>
43-c
44-b
45-c
46-b
47-b
48-c
49-d
50-a

والله اعلم ....

أموون66
2014- 12- 18, 10:47 PM
والله ان المراجعة زينه وشينه ..
بس ياليت تكملون الحل ويكون صحيح

زينه للي حالين وشينه للجايبين العيد ،،،،،،،،الله يستر :060:

نيف1
2014- 12- 18, 10:49 PM
بصراحه الاسئله صعبه جدا
الله لا يوفقه
لا اسئله مشابه للأعوام السابقه ولا تسهيل للطلبه

رعد نجد
2014- 12- 18, 11:04 PM
بصراحه الاسئله صعبه جدا
الله لا يوفقه
لا اسئله مشابه للأعوام السابقه ولا تسهيل للطلبه


لا حد يجي ويقول اننا ماذاكرنا صامين المراجعه صم واسئلة الواجبات واسئلة المراجعه

وفي النهايه مر سؤالين على استحياء

الله يجعلها بين السامع والدامع لاتخطي ولاتبطي

كنت متأمل اني بتخرج هذا الترم

اسئله فيها نوع من التحدي وفرض القوة الجبريه

Roo799
2014- 12- 18, 11:26 PM
الاجوية هذي متاكدين انها صح ؟؟؟؟؟؟؟؟؟؟؟
ارجوكم تأكدوا

رعد نجد
2014- 12- 18, 11:30 PM
الاجوية هذي متاكدين انها صح ؟؟؟؟؟؟؟؟؟؟؟
ارجوكم تأكدوا


ههههههههههههههههه

:53:
جاك اللي جاني


ان كانها صح فا العلم به علم عسى الله يزينها


لاوحسايف كنت متأمل اتخرج هالترم

صفية99
2014- 12- 19, 12:02 AM
تكفوووووون نبي الحل

خريجة ثانوي2014
2014- 12- 19, 12:07 AM
يعطيكم العافيه ...وش نستفيد من الحل عشان اعرف اخطائي و اصير نفسيه و الله ايش؟؟؟:Cry111::Cry111::Cry111::Cry111:

سـلام الورد
2014- 12- 19, 12:43 AM
1-c
2-b
3-a
4-d
5-c…….. I think
6-
7-
8-c
9-c
10-b
11-d
12-goes
13-
14-
15-
16-
17-
18-
19-
20-b
21-
22-c
23-c
24-
25-
26-b
27-a
28-c……I think.
29-b……… I think ….
30-
31-
32-
33-
34-
35-
36-
37-
38-d
39-
40-
41-a
42-
43-c
44-b
45-
46-d… I think …
47-
48-
49-d
50-a


اللي جاوبتها ميه بالميه
واللي م شفتها م جاوبتها

عيوشه محمد
2014- 12- 19, 12:54 AM
والله الاسئله أسهل من هيك مافي...بعدين هو قال الدكتور ذاكرو من المحتوى. .وماطلع عن اسئله المحتوى بشي يلي ذاكر لح يلاقيها سهله

Reem13
2014- 12- 19, 01:42 AM
جواب 50 قلتوا likes وهو قال إنها nonaction? ? تصير like ماتغير..

aseel..k
2014- 12- 19, 03:24 AM
الصراحة الأسئلة فيها من السهل والصعب
أنا كنت متأكدة من حلي 40 سؤال صح 100% وبعد المراجعة بالملتقى طلع نصها خطأ لأن الأسئلة فيها من اللخبطة ويبيلها تركيز شديد

بالنسبة لي كنت دارسة الإنجليزي 6 مستويات وعارفتة
بس أحس الأسئلة ماتصلح لمستوى أول أبدآآ

عندكم Article
اللي هي شيئين الأول the
والثاني a/an
أنا متأكدة منها 100% وبالأخير طلعت فقط a/an
فية غلط صراحة أنا ماعجبتني الأسئلة ومرة مقهورة من الدكتور المفروض سهلها على المسلمين هذا أول مستوى أجل الباقي وش بيسوون


مانبي A+ أهم شيء نعدي وبس الله يوفقنا ويسهل علينا

ابو أميرة
2014- 12- 19, 04:09 AM
من جد هذا اول مستوى انتساب و أسأله زي كذا .


سدت نفس من جد .

بنت الليث
2014- 12- 19, 04:17 AM
انا حامله هالمادة الكريهه الى نفسي وهالدكتور زاد الطين بله حسبي الله ونعم الوكيل بس

المفروض يعملون لنا استثناء عن هالماده زي الثانويه

دكاتره الانجليزي يحسبونا زيهم فاهمين يا اخي فكر فينا حنا طلبه انا من شفته يبربر لنا بدون عربي غسلت يدي

Reem_mahfouz
2014- 12- 19, 04:04 PM
جواب 50 قلتوا likes وهو قال إنها nonaction? ? تصير like ماتغير..

nonaction ما تزيد عليها ing بس ال s عادي

Reem_mahfouz
2014- 12- 19, 04:12 PM
الصراحة الأسئلة فيها من السهل والصعب
أنا كنت متأكدة من حلي 40 سؤال صح 100% وبعد المراجعة بالملتقى طلع نصها خطأ لأن الأسئلة فيها من اللخبطة ويبيلها تركيز شديد

بالنسبة لي كنت دارسة الإنجليزي 6 مستويات وعارفتة
بس أحس الأسئلة ماتصلح لمستوى أول أبدآآ

عندكم Article
اللي هي شيئين الأول the
والثاني a/an
أنا متأكدة منها 100% وبالأخير طلعت فقط a/an
فية غلط صراحة أنا ماعجبتني الأسئلة ومرة مقهورة من الدكتور المفروض سهلها على المسلمين هذا أول مستوى أجل الباقي وش بيسوون


مانبي A+ أهم شيء نعدي وبس الله يوفقنا ويسهل علينا

اجابتك صحيحة
الاجابة موجودة في lecture 13

English has two articles: the and a/an

ابوفيصل 2012
2014- 12- 19, 04:15 PM
الاجابات اللي حلتوها ما طمني انا اغلب اختياراتي ب

بنت الأحساااء
2014- 12- 19, 05:28 PM
أصعب اختبار

بنت الأحساااء
2014- 12- 19, 05:41 PM
كم النموذج هذا

بنت الأحساااء
2014- 12- 19, 05:42 PM
الصراحة الأسئلة فيها من السهل والصعب
أنا كنت متأكدة من حلي 40 سؤال صح 100% وبعد المراجعة بالملتقى طلع نصها خطأ لأن الأسئلة فيها من اللخبطة ويبيلها تركيز شديد

بالنسبة لي كنت دارسة الإنجليزي 6 مستويات وعارفتة
بس أحس الأسئلة ماتصلح لمستوى أول أبدآآ

عندكم Article
اللي هي شيئين الأول the
والثاني a/an
أنا متأكدة منها 100% وبالأخير طلعت فقط a/an
فية غلط صراحة أنا ماعجبتني الأسئلة ومرة مقهورة من الدكتور المفروض سهلها على المسلمين هذا أول مستوى أجل الباقي وش بيسوون


مانبي A+ أهم شيء نعدي وبس الله يوفقنا ويسهل علينا
:verycute:

محتـويني
2014- 12- 19, 05:54 PM
جعل من جابك في الجنه
وجزاكم الله خير جميعا

bint alkaldi
2014- 12- 19, 06:13 PM
الحمد لله عندي غلط واحد بس لا وأنا حطيت صح بعدين رجعت شطبت يالله الحمد لله .. ~

أم ريوف
2014- 12- 19, 07:15 PM
الصراحة الأسئلة فيها من السهل والصعب
أنا كنت متأكدة من حلي 40 سؤال صح 100% وبعد المراجعة بالملتقى طلع نصها خطأ لأن الأسئلة فيها من اللخبطة ويبيلها تركيز شديد

بالنسبة لي كنت دارسة الإنجليزي 6 مستويات وعارفتة
بس أحس الأسئلة ماتصلح لمستوى أول أبدآآ

عندكم Article
اللي هي شيئين الأول the
والثاني a/an
أنا متأكدة منها 100% وبالأخير طلعت فقط a/an
فية غلط صراحة أنا ماعجبتني الأسئلة ومرة مقهورة من الدكتور المفروض سهلها على المسلمين هذا أول مستوى أجل الباقي وش بيسوون


مانبي A+ أهم شيء نعدي وبس الله يوفقنا ويسهل علينا



الحين جاوبه a/an
ولا a/an/ the
احتررررت ؟؟؟:000:

Reem13
2014- 12- 19, 08:41 PM
والله انا كل تفكيري بالمعدل :(

rozaley
2014- 12- 19, 08:59 PM
صبايا بالنسبة للسؤال
how.........drink water
شو كان الجواب؟
how much
how often
بليز يلي بيعرف يخبرنا

Basomi1
2014- 12- 19, 09:21 PM
How much

Basomi1
2014- 12- 19, 09:42 PM
How much

Basomi1
2014- 12- 19, 09:43 PM
جواب 46 d وليس b

Basomi1
2014- 12- 19, 09:49 PM
جواب 50 b ما نضيف ع الفعل اي شيء .

Predominant
2014- 12- 19, 11:36 PM
الصراحة الأسئلة فيها من السهل والصعب
أنا كنت متأكدة من حلي 40 سؤال صح 100% وبعد المراجعة بالملتقى طلع نصها خطأ لأن الأسئلة فيها من اللخبطة ويبيلها تركيز شديد

بالنسبة لي كنت دارسة الإنجليزي 6 مستويات وعارفتة
بس أحس الأسئلة ماتصلح لمستوى أول أبدآآ

عندكم Article
اللي هي شيئين الأول the
والثاني a/an
أنا متأكدة منها 100% وبالأخير طلعت فقط a/an
فية غلط صراحة أنا ماعجبتني الأسئلة ومرة مقهورة من الدكتور المفروض سهلها على المسلمين هذا أول مستوى أجل الباقي وش بيسوون


مانبي A+ أهم شيء نعدي وبس الله يوفقنا ويسهل علينا

a , an) indefinite articles)
the : definite articles
والسؤال كان: English has two articles ما حدد إذا المطلوب(المعرفة أو النكرة)
وبالتالي يكون الجواب الصح (a/an-the)

وعلشان تفهموها اكثر
اللغة الانكليزية لها نوعان من أدوات التعريف
1- the تستخدم قبل الاسم المعرف بغض النظر إذا كان مفرد أو جمع
2-a/an تستخدمان قبل الأسم المفرد غير المحدد والفرق بينهم أنه
a تستخدم قبل الأسم المفرد بشرط أن يكون حرفه الأول من غير حروف العلة
an تستخدم قبل الاسم المفرد الي حرفه الأخير حرف علة
حروف العلة ( a,e,o,u.i)

mohammed -sa
2014- 12- 20, 02:06 AM
صح كلامك ما حدد والسؤال هذا حاطه للناس الملمه بالغه
وانا مع ألي يقول فيه شوية صعوبه دام انه مستوى اول للي ما عنده خلفيه بالغه تقريبا فيه عشره اسئلها مخليها صعبه . وان شاءالله ما احد يحمل الماده

Predominant
2014- 12- 20, 08:36 AM
صح كلامك ما حدد والسؤال هذا حاطه للناس الملمه بالغه
وانا مع ألي يقول فيه شوية صعوبه دام انه مستوى اول للي ما عنده خلفيه بالغه تقريبا فيه عشره اسئلها مخليها صعبه . وان شاءالله ما احد يحمل الماده


وللتأكيد هذه محاضرة كاملة عن هالموضوع فيها شرح كامل
Using Articles

What is an article? Basically, an article is an adjective. Like adjectives, articles modify nouns.

English has two articles: the and a/an. The is used to refer to specific or particular nouns; a/an is used to modify non-specific or non-particular nouns. We call the the definite article and a/an the indefinite article.

the = definite article

a/an = indefinite article

For example, if I say, "Let's read the book," I mean a specific book. If I say, "Let's read a book," I mean any book rather than a specific book.

Here's another way to explain it: The is used to refer to a specific or particular member of a group. For example, "I just saw the most popular movie of the year." There are many movies, but only one particular movie is the most popular. Therefore, we use the.

"A/an" is used to refer to a non-specific or non-particular member of the group. For example, "I would like to go see a movie." Here, we're not talking about a specific movie. We're talking about any movie. There are many movies, and I want to see any movie. I don't have a specific one in mind.

Let's look at each kind of article a little more closely.

Indefinite Articles: a and an

"A" and "an" signal that the noun modified is indefinite, referring to any member of a group. For example:

"My daughter really wants a dog for Christmas." This refers to any dog. We don't know which dog because we haven't found the dog yet.
"Somebody call a policeman!" This refers to any policeman. We don't need a specific policeman; we need any policeman who is available.
"When I was at the zoo, I saw an elephant!" Here, we're talking about a single, non-specific thing, in this case an elephant. There are probably several elephants at the zoo, but there's only one we're talking about here.
Remember, using a or an depends on the sound that begins the next word. So...

a + singular noun beginning with a consonant: a boy; a car; a bike; a zoo; a dog
an + singular noun beginning with a vowel: an elephant; an egg; an apple; an idiot; an orphan
a + singular noun beginning with a consonant sound: a user (sounds like 'yoo-zer,' i.e. begins with a consonant 'y' sound, so 'a' is used); a university; a unicycle
an + nouns starting with silent "h": an hour
a + nouns starting with a pronounced "h": a horse
In some cases where "h" is pronounced, such as "historical," you can use an. However, a is more commonly used and preferred.
A historical event is worth recording.
Remember that these rules also apply when you use acronyms:

Introductory Composition at Purdue (ICaP) handles first-year writing at the University. Therefore, an ICaP memo generally discusses issues concerning English 106 instructors.
Another case where this rule applies is when acronyms start with consonant letters but have vowel sounds:

An MSDS (material safety data sheet) was used to record the data. An SPCC plan (Spill Prevention Control and Countermeasures plan) will help us prepare for the worst.
If the noun is modified by an adjective, the choice between a and an depends on the initial sound of the adjective that immediately follows the article:

a broken egg
an unusual problem
a European country (sounds like 'yer-o-pi-an,' i.e. begins with consonant 'y' sound)
Remember, too, that in English, the indefinite articles are used to indicate membership in a group:

I am a teacher. (I am a member of a large group known as teachers.)
Brian is an Irishman. (Brian is a member of the people known as Irish.)
Seiko is a practicing Buddhist. (Seiko is a member of the group of people known as Buddhists.)
Definite Article: the

The definite article is used before singular and plural nouns when the noun is specific or particular. The signals that the noun is definite, that it refers to a particular member of a group. For example:

"The dog that bit me ran away." Here, we're talking about a specific dog, the dog that bit me.

"I was happy to see the policeman who saved my cat!" Here, we're talking about a particular policeman. Even if we don't know the policeman's name, it's still a particular policeman because it is the one who saved the cat.

"I saw the elephant at the zoo." Here, we're talking about a specific noun. Probably there is only one elephant at the zoo.

Count and Noncount Nouns

The can be used with noncount nouns, or the article can be omitted entirely.

"I love to sail over the water" (some specific body of water) or "I love to sail over water" (any water).
"He spilled the milk all over the floor" (some specific milk, perhaps the milk you bought earlier that day) or "He spilled milk all over the floor" (any milk).
"A/an" can be used only with count nouns.

"I need a bottle of water."
"I need a new glass of milk."
Most of the time, you can't say, "She wants a water," unless you're implying, say, a bottle of water.

Geographical use of the

There are some specific rules for using the with geographical nouns.

Do not use the before:

names of most countries/territories: Italy, Mexico, Bolivia; however, the Netherlands, the Dominican Republic, the Philippines, the United States
names of cities, towns, or states: Seoul, Manitoba, Miami
names of streets: Washington Blvd., Main St.
names of lakes and bays: Lake Titicaca, Lake Erie except with a group of lakes like the Great Lakes
names of mountains: Mount Everest, Mount Fuji except with ranges of mountains like the Andes or the Rockies or unusual names like the Matterhorn
names of continents (Asia, Europe)
names of islands (Easter Island, Maui, Key West) except with island chains like the Aleutians, the Hebrides, or the Canary Islands
Do use the before:

names of rivers, oceans and seas: the Nile, the Pacific
points on the globe: the Equator, the North Pole
geographical areas: the Middle East, the West
deserts, forests, gulfs, and peninsulas: the Sahara, the Persian Gulf, the Black Forest, the Iberian Peninsula
Omission of Articles

Some common types of nouns that don't take an article are:

Names of languages and nationalities: Chinese, English, Spanish, Russian (unless you are referring to the population of the nation: "The Spanish are known for their warm hospitality.")
Names of sports: volleyball, hockey, baseball
Names of academic subjects: mathematics, biology, history, computer science

ماجد 2207
2014- 12- 20, 11:47 AM
ياليت يا اخوان احد يجمع الاسئله بملف pdf محلوله

امل محسن
2014- 12- 20, 05:13 PM
تكفووون نبيها pdfمحلووله طلبتكم هذي ٣مرره اختبر ������الله يستر

fakhriyah
2014- 12- 20, 05:52 PM
انا كنت بصور قالو ممنوع :(
المهم :
1- go to .......work
correct answer : zero article
2- noun is a word that means
a- aperson
b- a thing
c- a person and a thing
d- a person , a thing , an activity , a place
the correct answer (as i picked ) is : d
3- my ..... is 83.4%
the correct answer is : average
4-" uncooked" word has the same meaning of ....
the correct answer is :raw
5- ...is my car over there
the wright answer is : that
6- there are two articles in english :
the correct answer is : a/an
7- horse is... animal ...
the correct answer is : a /an
8- huda ....english
the correct answer is : likes
9- we saw the accident when we .....to school
the correct answer is : were going
10 - the right contruction for" i am not" is
the correct answer is i'm not
11- we live in a big house ,...house is very old and has a balcony
the correct answer is : the
12- everybody is out to do ..... best
the correct answer is :his
13- when a student parks a car on campus .........should have a parking sticker
the correct answer is : he or she
14- سؤال عن in و on ,وat وكان حله in علشان شهر
15- the water usually.... at 100 digree selsius
the correct answer is : boils
16- the men .......in the building
the correct answer is: are working
17- he was very happy , he made ...moneyfrom the project
the correct answer (as i picked ) is : a few
18- there are only ...people i can trust
the correct answer (as i picked ) is : a few
18- ....."the word " beautiful" has the same meaning of the word
the correct answer is : attractive

وبس هذا اللي اتذكره :14::42::42::34:
والقطع جاب القطعة حقت الفرق بين الاولاد والبنات وخلاها سؤالين وكان فيه قطعتين ثانيات ناسيتهم :p بس عالعموم الله يعطيه العافية والله ما كان صعب لهالدرجة :(300)::(47):

fakhriyah
2014- 12- 20, 06:01 PM
واتوقع والله اعلم اني غلطت بالسؤال حق
he was very happy , he made .... money in the last project
:Cry111:

reemat00
2014- 12- 20, 06:20 PM
وش تبون بالاجوبه تنغثون خلوكم عالنحو التطبيقي بكره فيس يبكي ..

Predominant
2014- 12- 20, 06:29 PM
انا كنت بصور قالو ممنوع :(
المهم :
1- go to .......work
correct answer : zero article
2- noun is a word that means
a- aperson
b- a thing
c- a person and a thing
d- a person , a thing , an activity , a place
the correct answer (as i picked ) is : d
3- my ..... is 83.4%
the correct answer is : average
4-" uncooked" word has the same meaning of ....
the correct answer is :raw
5- ...is my car over there
the wright answer is : that
6- there are two articles in english :
the correct answer is : a/an
7- horse is... animal ...
the correct answer is : a /an
8- huda ....english
the correct answer is : likes
9- we saw the accident when we .....to school
the correct answer is : were going
10 - the right contruction for" i am not" is
the correct answer is i'm not
11- we live in a big house ,...house is very old and has a balcony
the correct answer is : the
12- everybody is out to do ..... best
the correct answer is :his
13- when a student parks a car on campus .........should have a parking sticker
the correct answer is : he or she
14- سؤال عن in و on ,وat وكان حله in علشان شهر
15- the water usually.... at 100 digree selsius
the correct answer is : boils
16- the men .......in the building
the correct answer is: are working
17- he was very happy , he made ...moneyfrom the project
the correct answer (as i picked ) is : a few
18- there are only ...people i can trust
the correct answer (as i picked ) is : a few
18- ....."the word " beautiful" has the same meaning of the word
the correct answer is : attractive

وبس هذا اللي اتذكره :14::42::42::34:
والقطع جاب القطعة حقت الفرق بين الاولاد والبنات وخلاها سؤالين وكان فيه قطعتين ثانيات ناسيتهم :p بس عالعموم الله يعطيه العافية والله ما كان صعب لهالدرجة :(300)::(47):

رقم 6 الجواب الصح هو the - a/an

fakhriyah
2014- 12- 21, 01:24 AM
رقم 6 الجواب الصح هو the - a/an

بس الارتكلز اثنين بس !!

بنت الأحساااء
2014- 12- 21, 01:28 AM
خلونا نراسل الدكتور وتكثر الشكاوى على صعوبة الإسالة وأنها معقدة على ناس توهم في بداية المشوار
لعل وعسى يجيب نتيجة

Predominant
2014- 12- 21, 05:00 AM
بس الارتكلز اثنين بس !!

هذا الغلط الي وقع فيه أغلب الطلاب أختي الكريمة لما شافوا كلمة two افتكروا أنو العدد 2 راجع لِ a/an
بس الصح أنو2 يعود على أنواع أدوات التعريف 1- المعرفة للمفرد والجمع"the "
2-الغير معرفة للمفرد "a/an"
وأنا جبت مقالة كاملة توضح كل ما يتعلق بأدوات التعريف ولونت بالأحمر السؤال الي جانا بالامتحان برد سابق ورح ارجع حطها هون للمعلومة والإفادة




Using Articles

What is an article? Basically, an article is an adjective. Like adjectives, articles modify nouns.

English has two articles: the and a/an. The is used to refer to specific or particular nouns; a/an is used to modify non-specific or non-particular nouns. We call the the definite article and a/an the indefinite article.

the = definite article

a/an = indefinite article

For example, if I say, "Let's read the book," I mean a specific book. If I say, "Let's read a book," I mean any book rather than a specific book.

Here's another way to explain it: The is used to refer to a specific or particular member of a group. For example, "I just saw the most popular movie of the year." There are many movies, but only one particular movie is the most popular. Therefore, we use the.

"A/an" is used to refer to a non-specific or non-particular member of the group. For example, "I would like to go see a movie." Here, we're not talking about a specific movie. We're talking about any movie. There are many movies, and I want to see any movie. I don't have a specific one in mind.

Let's look at each kind of article a little more closely.

Indefinite Articles: a and an

"A" and "an" signal that the noun modified is indefinite, referring to any member of a group. For example:

"My daughter really wants a dog for Christmas." This refers to any dog. We don't know which dog because we haven't found the dog yet.
"Somebody call a policeman!" This refers to any policeman. We don't need a specific policeman; we need any policeman who is available.
"When I was at the zoo, I saw an elephant!" Here, we're talking about a single, non-specific thing, in this case an elephant. There are probably several elephants at the zoo, but there's only one we're talking about here.
Remember, using a or an depends on the sound that begins the next word. So...

a + singular noun beginning with a consonant: a boy; a car; a bike; a zoo; a dog
an + singular noun beginning with a vowel: an elephant; an egg; an apple; an idiot; an orphan
a + singular noun beginning with a consonant sound: a user (sounds like 'yoo-zer,' i.e. begins with a consonant 'y' sound, so 'a' is used); a university; a unicycle
an + nouns starting with silent "h": an hour
a + nouns starting with a pronounced "h": a horse
In some cases where "h" is pronounced, such as "historical," you can use an. However, a is more commonly used and preferred.
A historical event is worth recording.
Remember that these rules also apply when you use acronyms:

Introductory Composition at Purdue (ICaP) handles first-year writing at the University. Therefore, an ICaP memo generally discusses issues concerning English 106 instructors.
Another case where this rule applies is when acronyms start with consonant letters but have vowel sounds:

An MSDS (material safety data sheet) was used to record the data. An SPCC plan (Spill Prevention Control and Countermeasures plan) will help us prepare for the worst.
If the noun is modified by an adjective, the choice between a and an depends on the initial sound of the adjective that immediately follows the article:

a broken egg
an unusual problem
a European country (sounds like 'yer-o-pi-an,' i.e. begins with consonant 'y' sound)
Remember, too, that in English, the indefinite articles are used to indicate membership in a group:

I am a teacher. (I am a member of a large group known as teachers.)
Brian is an Irishman. (Brian is a member of the people known as Irish.)
Seiko is a practicing Buddhist. (Seiko is a member of the group of people known as Buddhists.)
Definite Article: the

The definite article is used before singular and plural nouns when the noun is specific or particular. The signals that the noun is definite, that it refers to a particular member of a group. For example:

"The dog that bit me ran away." Here, we're talking about a specific dog, the dog that bit me.

"I was happy to see the policeman who saved my cat!" Here, we're talking about a particular policeman. Even if we don't know the policeman's name, it's still a particular policeman because it is the one who saved the cat.

"I saw the elephant at the zoo." Here, we're talking about a specific noun. Probably there is only one elephant at the zoo.

Count and Noncount Nouns

The can be used with noncount nouns, or the article can be omitted entirely.

"I love to sail over the water" (some specific body of water) or "I love to sail over water" (any water).
"He spilled the milk all over the floor" (some specific milk, perhaps the milk you bought earlier that day) or "He spilled milk all over the floor" (any milk).
"A/an" can be used only with count nouns.

"I need a bottle of water."
"I need a new glass of milk."
Most of the time, you can't say, "She wants a water," unless you're implying, say, a bottle of water.

Geographical use of the

There are some specific rules for using the with geographical nouns.

Do not use the before:

names of most countries/territories: Italy, Mexico, Bolivia; however, the Netherlands, the Dominican Republic, the Philippines, the United States
names of cities, towns, or states: Seoul, Manitoba, Miami
names of streets: Washington Blvd., Main St.
names of lakes and bays: Lake Titicaca, Lake Erie except with a group of lakes like the Great Lakes
names of mountains: Mount Everest, Mount Fuji except with ranges of mountains like the Andes or the Rockies or unusual names like the Matterhorn
names of continents (Asia, Europe)
names of islands (Easter Island, Maui, Key West) except with island chains like the Aleutians, the Hebrides, or the Canary Islands
Do use the before:

names of rivers, oceans and seas: the Nile, the Pacific
points on the globe: the Equator, the North Pole
geographical areas: the Middle East, the West
deserts, forests, gulfs, and peninsulas: the Sahara, the Persian Gulf, the Black Forest, the Iberian Peninsula
Omission of Articles

Some common types of nouns that don't take an article are:

Names of languages and nationalities: Chinese, English, Spanish, Russian (unless you are referring to the population of the nation: "The Spanish are known for their warm hospitality.")
Names of sports: volleyball, hockey, baseball
Names of academic subjects: mathematics, biology, history, computer science