In light of my brief attempt to define infinitives today while discussing our style analysis of Pamuk's speech, I feel compelled to spend one blog post articulating more clearly what is meant by "infinitive" and providing some examples of its use.
An infinitive is the original, most basic form of a verb. It consists of to and a verb's base form. (To, of course, is what most of us would identify as a preposition, as in to the store, but when it precedes a base form of a verb to form an infinitive, it's called a "particle" instead.) Here are some examples of infinitives:
The metaphor I use in explaining infinitives is to think of an infinitive as the "basic" model of a verb that you receive when you purchase one from an online retailer. The verb arrives in your mailbox "packaged" as an infinitive and accompanied by instructions showing you how to "mold" the infinitive into a number of different verb forms. These forms are what grammarians call the principal parts of a verb, and every verb has five. Let's look at an example—here are the principal parts of the verb give:
Base (or Present): give
Present Third-Person Singular: gives
Past Participle: given
Present Participle: giving
For something a little more challenging, let's try the most widely used verb in the English language: be. What makes be slightly harder to work with is the fact that it can be more extensively conjugated than other verbs. While every other verb has a base and one additional present form, be has three additional present forms. Further complicating matters, it also has two different past forms. Here's how this verb would be mapped out:
Present: am (first-person singular), is (third-person singular), and are (second-person singular or plural as well as third-person plural)
Past: was (first- or third-person singular) and were (third-person plural)
Past Participle: been
Present Participle: being
Anyway, remember—when you order a verb from an online store, it arrives in your mailbox packaged as an infinitive, but you can feel free to mold it into other forms (any of the principal parts) to fit your sentences' needs.
Okay, now, what about the infinitive itself? How is that used in sentences? There are three ways.
1. Using an infinitive as an adjective.
An infinitive can function as an adjective in a sentence. Here's an example:
In light of my brief attempt to define infinitives today...
This probably looks familiar! Yes, the first sentence I wrote in this post contains an infinitive (to define), and it is functioning as an adjective. It modifies the noun attempt by telling us which attempt I'm talking about. Remember that adjectives modify nouns by describing them or specifying them, and specifying which attempt I mean is precisely what the infinitive to define does. Also, don't be fooled by an adjective's post-noun position. Recall that sometimes adjectives can and do come after the nouns they modify.
2. Using an infinitive as an adverb.
An infinitive can function as an adverb in a sentence. Here's an example:
Clark went home to relax.
Here, the infinitive to relax is fulfilling the role of an adverb by telling us why Clark went home. Remember that adverbs most often modify verbs by telling how, where, when, or why an action takes place, and telling why Clark went home is precisely what the infinitive to relax does.
3. Using an infinitive as a noun.
As I briefly pointed out today, an infinitive can function as a noun in a sentence. Here's an example:
To stay is a bad idea.
Here, the infinitive to stay is acting as a noun and can therefore fulfill the role of subject in this sentence. When you look at a sentence like this and try to determine the role of the infinitive, it may be helpful to read it to yourself while substituting the infinitive with a pronoun like "something." Thus, the sentence would read, "Something is a bad idea." That "something" would be, obviously, a noun as well as the subject of the sentence (since you can see that the only thing remaining is the predicate).
So, there you have it! I hope this has made infinitives at least somewhat clearer for you! If you have any further questions about infinitives and their uses, feel free to ask in the comments. :)