What is a determiner? Simply put, in English, a determiner is a word that introduces a noun. It always comes before a noun, not after, and it also comes before any other adjectives used to describe the noun.
Determiners are required before a singular noun but are optional when it comes to introducing plural nouns. For example, consider the placement and usage of the common determiner the in the sentences below:
In every example, the determiner is placed before the noun or noun phrase, regardless of whether the noun in the subject or predicate. In the first example, it comes directly before the noun, but in the second example, it comes before the adjective ("chocolate") that describes the noun ("cookie").
Note also that in the third example there is no determiner, as determiners are optional for plural nouns and noun phrases. When you want to discuss the noun in general (i.e., all metal cans), you don't need a determiner for plural nouns. However, the fourth example shows that you may add a determiner to refer to specific nouns (i.e., the metal cans right here).
Articles are among the most common of the determiners. There are three singular articles: a, an, and the. Articles specify (or determine) which noun the speaker is referring to. A and an are indefinite articles and are used when you are talking about a general version of the noun. For example:
In these examples, the sentence is talking about dogs or ostriches in general, meaning any dog. When your meaning is general, use an indefinite article. Note that a is used before words that begin with consonants while an is used before words beginning with vowels.
On the other hand, the is a definite article, meaning the speaker is referring to a specific noun. For example:
Here the speaker is referring to a particular dog and a particular restaurant. It's not a general category, but only one animal or place that's important. When your meaning is specific, use a definite article.
Demonstrative pronouns are also used as determiners in English. There are four of them: this, that, these and those. Demonstratives are used in a situation in which the speaker can point to the item they mean, making them even more specific than a definite article. For example:
This and these refer to items nearby; that and those refer to items far away. Note also that this and that are singular while these and those are plural.
Quantifiers are determiners that indicate how much or how little of the noun is being discussed. They include words such as all, few and many. For example:
Note that all can be used with other determiners to specify which particular items are meant (i.e. all the books in this pile). In this case, the quantifier always comes before the article or demonstrative. It's also possible to use all alone to refer to items generally, as in the second example.
When referring to a noun that belongs to someone or something, you can use possessive pronouns to show ownership. Possessive pronouns include my, your, his, her, its, our, and their. For example:
As always, the determiner comes before the noun and any modifying adjectives. In English, you can use the same possessive whether the noun it references is singular or plural.
How should you choose which determiner to use? For native English speakers, determining which determiner to use is second nature, since determiners are so often used in front of nouns.
For people learning English as a second language, it's helpful to remember a few rules:
Once you learn the dictionary definition of each determiner as you study English vocabulary, it becomes easy to select the determiner that best expresses your meaning, whether you want to show ownership, quantity or relative location.