When a glossary is asked for
In many subjects the glossary is an assignment of its own: collect the terms covered during the semester into one document. It is not copying the textbook — the meaning has to be put in your own words.
The second case is an appendix to independent work or coursework. Specialist terms go into a table at the end, and it counts towards the mark.
The third is for yourself. While writing a thesis or dissertation, having the terms in one file saves time later: you stop hunting for the same definition every time it comes up.
