The articles in English are the definite article the and the indefinite article a (which takes the alternate form an when followed by a vowel sound). They are the two most common determiners. The definite article is the default determiner when the speaker believes that the listener knows the identity of a common noun's referent (because it is obvious, because it is common knowledge, or because it was mentioned in the same sentence or an earlier sentence). The indefinite article is the default determiner for other singular, countable, common nouns, while no determiner is the default for other common nouns. Other determiners are used to add semantic information such as amount (many, a few), proximity (this, those), or possession (my, the government's).

English grammar requires that, in most cases, a singular, countable noun phrase start with a determiner. For example, I have a box is grammatically correct, but *I have box is not. The most common determiners are the articles the and a(n), which specify the presence or absence of definiteness of the noun. Other possible determiners include words like this, my, each and many. There are also cases where no determiner is required, as in the sentence John likes fast cars, where neither John nor fast cars includes a determiner.

The definite article the is the default when the referent of the noun phrase headed by a common noun is assumed to be unique or known from the context. For example, In the sentence The boy with glasses was looking at the moon, it is assumed that in the context the reference can only be to one boy and one moon. However, the definite article is not typically used:

The indefinite article a (before a consonant sound) or an (before a vowel sound) is used only with singular, countable nouns. It indicates that the referent of the noun phrase is one unspecified member of a class. For example, the sentence An ugly man was smoking a pipe does not specify the identity of the ugly man or pipe.

When referring to a particular date, the definite article the is typically used.

When referring to a day of the week, the indefinite article "a" or definite article "the" may be used, following the same guidelines of generality versus specificity.

No article is used with plural or uncountable nouns when the referent is indefinite (just as in the generic definite case described above). However, in such situations, the determiner some is often added (or any in negative contexts and in many questions). For example:

Additionally, articles are not normally used: