You might have noticed that secondary verbs are often (but not always) followed by 'to'. You probably also noticed that we've been highlighting the 'to' as part of the main verb. Why do we highlight it like that, rather than as something separate?
The short answer is, that's just how it is. And it's okay if you just want to leave it at that for now. But if you're interested in some pretty abstract word theory, read on.
Let's imagine we're writing a dictionary and we're adding the definition of is, are, was, am, been, and all the other forms of being verbs you can think of. We could give them all a separate entry, but paper and ink used to be pretty expensive, and when you think about it they all basically mean the same thing—something about 'being'.
Ok, you might think, let's just choose one of them and group them all under that word. But which one? All the options we've looked at have extra information baked in – like whether it's past or present tense, or whether we're speaking about one person or a few people.
The solution to this conundrum is the 'to' form (in this case, 'to be'). The 'to' form of a verb (called the infinitive) is considered the base form. This is because it doesn't have any tense or other kinds of inflection (like when we add -ing or -s or other sounds to a verb to make it grammatical).
So... why do the infinitive base forms of verbs need the 'to' attached? That's just English for you. Other languages often have one-word infinitives, like the French 'to be', which is ětre. So if we were speaking French, we wouldn't even be asking this question in the first place! 🤷🏽♂️