- Disgybl - A pupil.
Disgyblion - Pupils (plural).
'Many ...' -> Llawer + o + (soft mutation) plural...
Myfyriwr - A student
- Myfyrwyr - Students
From an American background, I am unclear as to the distinction between "pupil" and "student." We rarely use the former, and when we do, it is primarily a synonym of the latter.
I am not sure how to make the distinction clearly across different dialects of English, but the words are different in Welsh as in English - see above.
Where you use 'Student' in English, Myfyriwr is the Welsh word to use.
I'm a confused American too. I looked up the difference. Supposedly students are directly enrolled in a school but pupils can be either in a school or have private tutors. The confusion for us Americans is probably that none of us ever had private tutors, so all pupils are also students. Maybe tutors are a rich British thing.