I got into a conversation on Twitter this week about whether a Japanese word was a verb or a noun. The simplest way I could put it was that it couldn't be a 'to X' verb, because those all end in 'u'. This one ended in 'e'. It might have been a conjugated form of the verb – with the 'e', it would have been an informal imperative – but in this case it was a noun.
Then, I made a mistake. I started talking about another word, which coincidentally also had a 'u' at the end. When asked if this new word was a verb, I had to sheepishly say no. This confused the poor person I was talking to even more.
This is an example of a syllogism going wrong. The other person's logic was as follows:
All Japanese verbs end in 'u'.
This word ends in a 'u'.
So it must be a verb.
However, this leap of logic is actually a 'syllogistic fallacy'. That's what Wikipedia thinks the problem is, anyway.
It's true that all 'to X' verb forms end with a 'u', but not every Japanese word ending with 'u' is a verb. The only thing you can say for sure is that a word that doesn't end in 'u' is definitely not a 'to X' verb form.
It may be a noun. It's unlikely to be an adjective because those mainly end with 'i' or 'na'. And even then, Japanese doesn't employ the use of adjectives in a syntactic sense, they're more to do with semantics.
When I tell people that Japanese is a tough language to learn, they really need to believe me.
To try and make it easier to see, here's a quick list of some copywriting-related Japanese verbs: