In English, singular countable nouns usually cannot be used alone; they must be preceded by a word such as a, the, each or every.
e.g. a box
the person
each child
every tree
The words a, the, each and every are examples of a group of words which can be referred to as determiners. Such words, when used together with nouns, help to determine to which particular entities the nouns are referring. Determiners other than a and the are dealt with in detail in a separate chapter.
Singular countable nouns must usually be preceded by determiners even when the nouns are also preceded by various descriptive words.
e.g. a heavy, awkward box
the right person
each young child
every tall tree
The meanings of the words a and the are less specific than the meanings of the other determiners. A and the are sometimes referred to as articles. They are the determiners most frequently used with singular countable nouns.