adjective
BAD : Basement flats are often dark and moist.
GOOD : Basement flats are often dark and damp.
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moist = slightly wet, especially in a pleasant way: 'The bread was still nice and moist.' 'These plants prefer a warm, moist atmosphere.'
damp = slightly wet, especially in a cold and unpleasant way: 'Our hotel room felt cold and damp.' 'On damp days, we have to dry the washing indoors.'