Small plug for plural tags, at least in some use-contexts:
Increasingly there’s power in making tags function as tiddlers, where information about the tag-children gets listed, or displayed in a dynamic table, etc. (Even when the tag tiddler is Missing (lacking any field contents) I usually have a ViewTemplate element that offers an automatic overview of items under that tag.)
The use of a singular tag in this way is odd, and can lead to confusion. A plural tag is clearer. For example, all definitions are gathered under the tag “definitions,” and the tag pill nicely lists definitions, just as the tiddler itself serves as a clearing-house for definitions.
Given that the word “definition” itself might need to be defined or discussed, the place where definitions are gathered should be different from the specific tiddler for “definition”.
Though it may be mildly counter-intuitive at first if your habit while tagging is to think “This tiddler is a _ _ _ _”, the plural helps remind everyone that the tag can orient us to a set.
Cheers!