I would say it depends on the field. In STEM, you will probably have definitions that should be clear on the first occurrence and used afterward. There you can emphasize the term you define, like
We call a number positive when it is greater than 0
so it is clear which term you're actually defining. If a glossary or list of definitions is present, it is helpful when it contains every emphasized term. The other direction may or may not be useful depending on if the glossary is meant to contain everything needed or only the essential terms defined through the text. In the example above, you could also have a definition for number in the glossary, but you wouldn't want to emphasize it in this sentence because it is only used in the sentence but not defined there.