This is the thing that always confused the hell out of me basically. Like there’s no method or anything to it, if you come across a new word you just have to ask I guess? Like if I come across a new word in English I can just ask what it means, but I guess in French you have to ask what it means, and also what gender is this abstract concept or inanimate object? Which just feels really weird to me, I guess other people are just used to it.
The one that confused us the most learning Japanese was number counters: https://www.learn-japanese-adventure.com/japanese-numbers-counters.html
So ichi, ni, san, yo, go. Counting flat thin things? ichimai, nimai, sanmai, yomai etc. Counting long round things? ippon, nihon, sanbon, yonhon. They’re fairly regular prefixes so it’s quite easy to use. But when we were taught there was one for electronic things, which obviously started people going is an iPad a flat thin thing or an electronic thing? There was one for food, so is a cucumber a long round thing or a food thing? The main answer seemed to lie in Japanese people mostly dropping it in conversation because it’s confusing.