Determiners

Nouns can stand on their own in sentences such as:

Elephants like grass.

While it is true that you can use the plural noun elephants in this way, you cannot use the singular noun elephant. Elephant eats grass is not a complete clause. It needs something else. for example:

An elephant eats grass.

The commonest type of word to come before a noun in this way is an article: a / an / the.

There are several other words that serve a similar purpose: