Among the many strange features of the English language is the bare infinitive. We’re not talking about anything NSFW here. Infinitives are the basic forms of verbs. You might see them paired with the preposition to — to sit, to eat, to think — or you’ll see them standing alone. When the infinitive isn’t partnered with to, it’s called a bare infinitive.
Bare infinitives are common, but that doesn’t mean they don’t have weird rules. They are a part of the English language, after all. So even though most native speakers will use bare infinitives without thinking about it, let’s examine the rules.
When can you use a bare infinitive?
The tricky thing about bare infinitives — sometimes called zero infinitives — is that there isn’t a single hard and fast rule for them.
We'll take a look at the parts of speech and some examples you can use to remember when and where to use bare infinitives. We’ve italicized the bare infinitives just to clear things up. We've also included how the sentence would look if you didn't use a bare infinitive — in some cases, it's downright cringeworthy.
With auxiliaries (can, should, would, might)
You should wait for the next bus. (NOT You should to wait for the next bus.)
I would walk instead. (NOT I would to walk instead.)
After perception verbs (see, hear, feel)
I heard him come in this morning. (NOT I heard him to come in this morning.)
She saw them leave. (NOT She saw them to leave.)
After make or let
They made him read the passage again. (NOT They made him to read the passage again.)
She let him tell the story. (NOT She let him to tell the story.)
After had better
You had better be careful! (NOT You had better to be careful!)
After why
Why buy this one when that one is cheaper? (Why to buy this one when that one is cheaper?)
How do I remember the rules?
Did you find a pattern in the rules? Neither did we. You’ll probably need a few different mnemonics to remember all of the applications for bare infinitives if you're really dedicated to learning them.
Modals will cover a lot of uses of a bare infinitive. A modal is a word that expresses likelihood or intention. Can, could, may, might, must, will, would, shall, should, ought to, and had better are all modals. If a modal appears before the verb, it’s an infinitive. However, you wouldn’t say, “Can I to go now?” It just sounds wrong. So you drop out the “to” and use the bare infinitive with a modal.
Make, let, have, and other causative verbs are also used with bare infinitives. You can remember that if the initial verb causes the next one (He made me do it), then there’s probably a bare infinitive there.
Bare infinitives are frustrating. Even when trying to think up better ways to remember them, there’s no single rule or mnemonic to help with all of the different applications. If nothing else, you’ll notice them as you use them. Test out including to or leaving it out if you’re confused. Bare infinitives may not be used consistently with different parts of speech, but the words used with them don’t change. Once you know them, they’re there to stay.