Usage
start with a determiner.[1] For example, I have a box is grammatically correct, but *I have box[a] 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:
with generic nouns (plural or uncountable): cars have accelerators, happiness is contagious, referring to cars in general and happiness in general (compare the happiness I felt yesterday, specifying particular happiness);
with proper names: John, France, London, etc.
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.[2]
He was born on the 10th of May.
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.
He was born on a Thursday.
He was born on the Monday before Thanksgiving.
