I noticed that there's quite a lot of questions that are tagged with usage tag (398 as of now). This tag on it's own seems very broad too me. What does it really mean? Usage of what exactly? Wouldn't most of questions here be about some kind of usage? This tag pretty much always requires a second tag to explain it and narrow it down.
As a matter of fact, there's already a few other "usage" tags: kana-usage, word-usage and kanji-usage. They are not much used (12, 4 and 3 questions respectively). They seem to be more useful as in one tag they describe the problem and the area, e.g. kana-usage means problems with usage of kana.
I think that the usage should be discontinued. I'm not exactly sure what's the best way about it as it's used on so many questions and retagging them would bump them all up (am I right?) Maybe it can be not used on future questions?
Alternatively, if the community prefers, we can leave usage and make other tags synonyms.
Also, a similar problem has been already raised early on in this question: Consolidate "Word-choice" and "Usage" tags.
