It seems to me that the vocabulary tag is mostly superfluous.
I found this old post from 2010 which compares the tags words, which has since been rightfully discontinued, word-choice, single-word-requests and vocabulary. RegDwigнt asserts at the end that the words tag is a simple cop-out for someone who doesn't know which tag to use.
Of course, the state of the taxonomy has evolved since 2010. I am well aware that the tag is in the all-time top30 of used tags. However, it seems, that the vocabulary tag might be actually obsolete now. Every use of the tag - which is by the way not given by the tag wiki - seems to be covered by other tags.
More importantly, the tag info says:
This tag should be distinguished from:
- word-choice, which is for questions about choosing a word from a set of alternatives
- single-word-requests, which is for questions about finding a word to fit a meaning, when you don't yet have any alternatives to choose from
- meaning, which is for questions about definitions and nuances of meaning in a word or phrase
Naturally, that's not how the tag is used.
- 321 overlaps with single word requests
- 200 overlaps with word-choice
- 227 overlaps with the tags containing meaning
Looking at the questions tagged with vocabulary almost none besides the example questions seem to match the tag's intention.
Another indicator that the tag in its current state might be not that useful is that almost 30% of the vocabulary only tagged questions are closed which is higher than the overall rate.
As first step I edited the usage guidance of the vocabulary tag to match its intention as described in the old post and the example questions. Thankfully, that has since been approved.
What am I suggesting now?
As a second step, however, I want to ask if the tag vocabulary is necessary at all? Especially considering that we have a closing reason too broad and it seems to apply to most of the example questions.
P.S. It would be nice to get some insight by the people who actually use the tags. Especially the highly involved tag editors.