The quality of putting other people before yourself. This is the noun — the thing itself, not the person and not the action. So we say 'his unselfishness surprised everyone', 'an act of unselfishness', 'she showed great unselfishness'. It names a character trait, something you can have a lot of or a little of. Because it is a noun, it does not usually take 'a' or 'an' on its own: 'she has unselfishness' sounds odd; people say 'an act of unselfishness' or 'a rare unselfishness about her'. It turns up most in serious places — funeral speeches, awards, school reports, articles about volunteers and about sport. In ordinary conversation Taiwanese students will hear 'she's so unselfish' far more often than 'her unselfishness'. Worth knowing: many writers prefer 'selflessness', which sounds stronger and grander — unselfishness sounds more everyday and more human-sized, more like a good habit than a saintly virtue.