In English grammar, an antecedent is a word that will be replaced by another word later in the sentence. Most often the word replacing the antecedent is a pronoun. In the sentence, "When John went out in the rain, he got wet," "John" is the antecedent to the pronoun "he." Understanding the antecedent-word relationship is crucial to grasping how English works.
As you'll know if you followed the link in the intro, an antecedent is anything that happens before something else. Especially in older or more formal English prose, one might refer to one's ancestors or one's predecessors in a job as "my antecedents." The word also occurs in science, referring to an organism's evolutionary forebears.
In grammar, an antecedent is a word that another word refers back to. That word is technically called a proform, and while English allows for types of antecedents based on many parts of speech, such as pro-verbs and pro-adverbs, it is far more common for a pronoun to refer to an antecedent.
Taking the place of an antecedent is what a pronoun is for. Compare these two sentences:
When John comes inside, John will dry off with John's towel in John's bathroom.
When John comes inside, he will dry off with his towel in his bathroom.
The second sentence eliminates the unnecessary repetition of John's name by utilizing suitable pronouns.
Since the pronoun replaces the noun in the sentence, they have to agree with one another in number. If the antecedent is singular, then the pronoun that takes its place must also be singular:
John went out in the rain, so he got wet.
If the antecedent is plural, the pronoun must be plural:
John and Jane went out in the rain, so they got wet.
In the context of the second sentence, "John and Jane" are what is called a compound subject. This requires a plural pronoun. Compound subjects can be more complex than that, however.
When the antecedents are joined with "and," as with "John and Jane," the pronoun needs to be plural since it encompasses both of them.
By contrast, if "John or Jane" went out in the rain, the pronoun has to agree with the subject closest to the pronoun.
This is true whether the antecedent is singular or plural: "Either John or the weather forecasters messed up their prediction." The "their" agrees in number with the (plural) forecasters.
There are several rules concerning the use of indefinite pronouns as antecedents and the pronoun antecedent agreement.
The following indefinite pronouns are singular. As such, they need a singular pronoun:
An example of an indefinite antecedent taking a singular pronoun is: "Everything here has its own box."
By contrast, plural indefinites take on a plural pronoun. These are the plural indefinite pronouns:
As an example, take this sentence: "Several are there because of their looks."
Finally, an indefinite pronoun may be modified by a prepositional phrase. In such a case, the object of the phrase determines the agreement between the pronoun and its antecedent. These special indefinite pronouns include:
Look at these two sentences:
If the object is uncountable, like "flour," then the pronoun has to be singular (its). If the object is countable, like "gems", then the pronoun needs to be plural (their). For more help with this, review our article on countable and uncountable nouns.
This article was written to answer the simple question, "What is an antecedent in grammar?" That simple question's simple answer is "a word that will be replaced in later usage with another word." That word is most commonly a pronoun.
For more on how pronouns must agree with the nouns they replace, take a look at our article on pronoun agreement.