Everyone agrees on the eight parts of speech, except of course when there are nine. What is a part of speech? Well, here they are: adjective, adverb, conjunction, determiner, interjection, noun, pronoun, preposition, verb.
But what about a gerund, which is a verb participle acting as a noun? Is an article just a type of determiner, or does it count as a separate part of speech? And speaking of determiners: his, her, and their are determiners, right? Or are they possessive pronouns? It depends who1 you ask. And what about very? Why doesn’t it work like other adverbs?
If you invented a language, you might think to yourself: Let's have words for stuff, we'll call them nouns. And then you'd want words for doing things with stuff: We can call those verbs. You'd end up with a lot of rules describing how the language works, and you could make sure the language followed those rules.
But English wasn't invented.
All the rules we call grammar are an attempt to understand—and in some cases enforce—the way English works. But grammar can’t be completely true. Not only does the language continue to evolve, but we never got all the rules right in the first place. Grammar is our best explanation of how English works today, not a set of immutable laws that control the language. Although we’ve identified parts of speech to represent different species of words that we encounter, that taxonomy doesn't grapple well with cross-breeding.
Words that Don’t Fit
There are many words that don’t cooperate with recognized grammatical categories.
Is a gerund a noun, a verb, or something else? A gerund is a form of a verb that acts like a noun. The reason we don't promote it to a full “part of speech" is because we don't need to. We can understand what's happening without establishing a gerund as something that's neither a noun nor a verb. We just think of it as both: it’s kind of a noun about verbing.
What about modal verbs? A modal verb like might isn't a real verb. You can't say *I mighted all night. It seems more like an adverb, because it modifies a verb: I might run for office. But it isn't an adverb, because it doesn't work with adjectives: *My room is painted might green. With so many examples—can, could, may, must, should, have to, had better, and more—you'd think this would be a separate part of speech. But somehow it's a special kind of verb that you can't use as a verb.
Pronouns or determiners? A word like their is a determiner because it makes the noun that follows it more specific. Some people call these words possessive determiners, but they are also pronouns because they stand in for antecedents.2
The Very Problem
We use the word adverb to mean a word that can modify verbs, adjectives, or other adverbs. Very is an adverb. So why can't we say *I was very talking?3
If the rules determine how the language should behave, and the rules say that an adverb can modify a verb, then *I was very talking is correct by definition.4 If, on the other hand, grammatically correct means using English the way native speakers understand it, then *I was very talking is wrong.
If you believe that very talking5 is correct, you are either a weirdo or a prescriptivist: someone who believes that the rules are true and must be followed. If you believe very talking is weird—but you'd go along if people started saying it—you might be a descriptivist: someone who believes the rules must continue to adapt in order to reflect the way the language really works.
Drifting across Parts of Speech
When verbs are used as nouns, or vice versa, both prescriptivists and descriptivists get annoyed. But this reaction makes no sense.
Parts of speech are both imprecise and fluid. The above examples demonstrate that some words don’t fit neatly into a single part of speech. Furthermore, as words change or add to their roles over time, they escape their bonds and grow to occupy multiple parts of speech. There are many verbs that started as nouns, and the converse. It’s been happening for centuries.
It might bother people when a word starts to make such a transition, but that is just a sentimentality. Prescriptivists can rail against it for a while, if they must, but descriptivists must accept this kind of change without hesitation. And the prescriptivists always lose eventually.
Here's my ask.6 You can side7 with the descriptivists or the prescriptivists, but you can't have it both ways. If very talking sounds wrong to you, then you are a descriptivist; you have to welcome verbed nouns. If you’re a prescriptivist, same advice 100 years from now, I guess.
The next time someone mentions8 that they plan9 to “action10” something, stifle your reply11 that action is a noun.
Do parts of speech exist?
Sure, whom, if you wish. You’ll love the end of this article.
See The Danger of “It” for more about antecedents.
You might argue that very can modify verbs like interesting. In that context, interesting behaves as an adjective.
The prescriptivists will here say something about how very is an exception, the exception proves the rule, and that very actually strengthens the case for adverbs as a part of speech. I rebut: if you're a prescriptivist, don't you get to use the rules to determine how the language behaves? The exception proves the rule sounds descriptivist to me.
I am aware that very comes from verus (Latin for true) and that it's related to verily. You can indeed say I was verily talking. But you still can't say *I was very talking.
This one probably bothers you. That's because it's relatively new.
This one even bothers me! But I'm getting over it.