A trait is one particular quality in someone's character — one piece of what a person is like. Patience is a trait; stubbornness is a trait; a quick temper is a trait. The word is neutral in itself: a trait can be good or bad, and you show which by the words around it (an admirable trait, an annoying trait). What makes trait different from a plain word like quality is that it points at something lasting and typical, not a mood. Being sad today is not a trait; being someone who worries about everything is. It is a slightly formal word — you meet it in psychology, in biology, in book reviews and character descriptions — and in ordinary conversation people are more likely to say "that's just how she is". Two uses are worth knowing. In science, traits are the features passed from parents to children, and not only mental ones: eye colour, height, and the shape of a leaf are all traits, so the biology sense covers the body too. And there is a fixed phrase, personality trait, which is very common and simply makes the meaning explicit. The pronunciation is "trayt" and the final t is spoken; a few British speakers of an older generation still say "tray" in the French manner, but that now sounds unusual.