A yearning is the feeling itself — a deep, aching wish for something you cannot easily have. It usually goes with 'for' ('a yearning for home') or with 'to' ('a yearning to be understood'). You can count it: 'a yearning', 'these yearnings'; you can also use it uncountably: 'full of yearning'. Two things make it different from 'wish' or 'desire'. It is slow — a yearning lives in you for months or years, it does not arrive and leave in an afternoon. And it points at something out of reach, so it always carries a little sadness even when what you want is beautiful. That is why writers use it for homesickness, for lost love, for the past, and for the kind of longing that has no clear object at all — 'a strange yearning she could not name'. The same form is also the -ing form of the verb ('she was yearning for home') and can act as an adjective ('a yearning look' — a face that shows the feeling). It is a literary word; in normal talk Taiwanese students will more often say 'I really miss...' or 'I've always wanted...'.