SE sites generally evolve rather than being planned in advance and this is most evident in the tagging.
People also get used to how the tagging system works and this makes it harder and harder to change as a site matures.
So while we can learn from the structure of ELU's tag system, we can also learn from mistakes made there that have gelled or crystallised and now persist despite not being the best way to do things.
For instance I strongly feel most tags including "word" are bad since they don't allow for idioms, set phrases, and other things we might think of as words but which are actually two or more words separated by spaces (echar de menos, nada que ver, etc). It's better to use "term" or just to leave out this part. Instead of "word usage" have either "term usage" or just "usage".
Another thing to keep in mind is that tag synonyms are not about English synonyms or Spanish synonyms, they are about making useful clusters of concepts. Whether "meanings" or "definitions" are exactly synonyms by the dictionary is not what's important. It's whether they would be used for ("characterise") the same kind of question. This sometimes means it can be tricky choosing the best name for the tag. But ugly tags can be renamed and the tag wiki excerpts are there to tell the users how to use the tags, especially when the tag name simply cannot explain it fully. And editors with enough rep should be retagging questions that new contributors had trouble tagging.
One more thing, most Stack Exchange sites have decided to go with plural tags rather than singular wherever this makes sense. (It doesn't always make sense). You might find my post on travel SE on this topic of interest: Tags should be plurals (with a few caveats).
Jeff Atwood also wrote a blog post back in August with some very good tips for good tagging: Improved Tagging