This is perhaps the hardest issue for second language learners. If you do not speak English as your first language, it may take a long time for you to master English articles and acquire native speakers' proficiency on the subject. If not sure about which article to use in a particular context, you can ask native speakers of English for help. However, don't expect them to be able explain why, unless they have studied linguistics, because it's more of a matter of intuition and convention than rules. Having said that, we have some guidelines that may be useful for you below.

1. Three Types of Articles

There are three types of English articles: indefinite articles ("a" or "an"), definite article ("the"), and zero article, as in:

2. Countable vs. Non-countable

Every singular, countable noun in English must have an article, whereas non-countable nouns and plural nouns do not require an article, as in:

In 2.1 and 2.2, you can see that "a car" and "a package" are countable nouns, thus requiring an article. However, in 2.3 and 2.4, "love" and "rain" are non-countable, therefore don't require an article. Finally, in 2.5, you have a plural noun, "English novels," and so you don't need an article.

3. Indefinite vs. Definite

The indefinite article ("a" or "an"), as its name suggests, is used when you have a singular countable noun that is unknown or not specific to the hearer, while the definite article ("the") is used when the hearer or the reader knows what specific noun you are talking about.

Using the examples above, you can see that in 1.1 and 1.2, the hearer cannot identify which specific notebook or a specific envelope the speaker is talking about: it could be any notebook or any envelope at the store, regardless of color, quality, and so on. However, in 1.3, the hearer knows which notebook and egg the speaker means—the specific notebook and envelope that they saw together the day before. The same explanation goes for 2.1 and 2.2 because "a new car" and "a package" are not direct references. That is, the hearer doesn't know what type of car it is, what color it has, or what the speaker receives in the mail.

On the other hand, if the speaker says "I received the package in the mail," the speaker believes that the hearer knows what package she or he is referring to.

4. Non-countable Nouns

As explained above, non-countable nouns (e.g., sugar, love, air, odor, water, anger, rain, light, darkness, etc.) do not require articles and they cannot be plural because there is no way you can count them. However, sometimes you can see non-countable nouns in the plural forms. This is in fact possible, but the plural forms of these non-countable nouns will exhibit differences in meanings. Here are some examples:

In all these examples, the non-countable nouns, when pluralized, differ in terms of meaning from their singular counterparts. In 4.1, the speaker actually refers not to the actual liquid drink, but the containers (i.e. "Can I have two cups of coffee?"). Similarly, in 4.2, the speaker refers to two pieces of hair (thus countable), rather than what a person has on his or her head, and in 4.3, the speaker is talking about types of wine, rather than the liquid drink itself. Finally, in 4.4, again, the speaker refers to an instance of course or program of education, perhaps through a good school or university. Compare this with "The president supports education," which means education in general, at every level. A good English dictionary will tell you which nouns are countable and which are not. We recommend the following dictionaries, specifically designed for second language learners, Oxford Advanced Learner's Dictionary (7th ed, 2005) or Longman: Dictionary of Contemporary English (4th ed, 2003).

5. Generic reference

Sometimes when writing you are not referring to just one member of the class or to specific entity; instead you want to refer to the whole class or every member of that class. In other words, you want to generalize what you are saying. There are two main ways to do so.

5.1 Use the plural form of noun

By pluralizing a noun, you can make it generic. This makes sense because the plural form indicates that there is more than one instance, and that what you say applies to all of these instances, as in:

In both of these examples, the nouns are in their plural forms ("apples", "oranges" "parents" and "children"), and so have generic meanings. That is, the speaker in 5.1.1 likes all apples and all oranges, while the speaker in 5.1.2 is making assumption that all parents—without exception—love their children. If you choose this option, do not forget to use the plural form of verb as well to agree with the plural subject noun.

5.2 Use the singular form with the definite article "the"

This option gives you the same generic reference as the plural option above. However, you have to be careful because this option is not as widely applicable as the first option. Some nouns cannot be used with the article "the" to signal generic reference.

Nouns that can be used with this option are usually those that refer to occupations (e.g., the student, the doctor, the patient, the soldier, the farmer, etc.), names of animals (e.g.,the lion, the turtle, etc.), body parts (e.g.,the lungs, the heart, etc), and human inventions (e.g.,the telephone, the computer, etc.). Choosing this option, you need to have a singular form of verb.

5.3 Use the singular form with the indefinite article "a" or "an"

This is the least used option because its use is very restricted. It is usually used when you explain the components of something, as in:

In both examples, the speaker is talking about the components of an essay and a bicycle in general; she or he means that every essay and every bicycle will have those components. Note that the generic reference above will be lost if you say, for example,

In these two sentences, the indefinite article just introduces a new information that the hearer or the reader has not heard before, and it does not refer to letters and bicycles in general.

The following sentence also sounds odd because of misuse of the indefinite article to signal generic reference:

5.3.5 A lion is an endangered animal.

For this sentence, you need to say "Lions are an endangered animal" or "The lion is an endangered animal". This is because "an endangered animal" includes the whole species, but by saying "a lion," you're just referring to a member of the whole species.

For more information on articles, we recommend that you check out Practical English Usage by Michael Swan, 3rd ed, 2006. This book gives very detailed, easy-to-understand rules on English articles.

Back to Grammar for ESL