We currently have a very frequently-used phrase tag, presumably used whenever the question is asking about anything regarding a phrase in English or Spanish. Should there be an analogous word tag for questions about a single word? If not, should the phrase tag even exist?
Generally speaking, I recommend following the tag structure of the English Language & Usage Stack Exchange. It's already gone through most of the issues, and I think it's done a good job with a difficult subject matter.
On French Language & Usage, we've largely followed EL&U's tagging practices from the start, and haven't regretted it. Of course, there will be minor differences, for example having to do with grammatical constructs that don't exist in the other language, or having [american-english] on one and [quebec] on the other.
Tags are created automatically when you tag your question with a tag that doesn't exist. If that tag is used, it will survive. If not, it will disappear by itself. So, since you can create them, try to use this feature wisely. Always prefer existing tags when they exist.
That said, there are many more words than phrases, so this last one defines something more specific than the former tag would... But I'd like to ask you a question, so you see it for yourself if the tags is needed: what questions could/would use the tag words?