aptness

affinity, aptitude, bent, disposition, inclination, leaning, mind-set, partiality, penchant, predilection, predisposition, proclivity, turn

custom, habit, pattern, practice (also practise), routine, wont

eccentricity, idiosyncrasy, oddity, peculiarity, quirk, singularity, trick

agreeableness, compatibility, congruity, harmoniousness

applicability, bearing, connection, justifiability, materiality, pertinence, relevance, relevancy, validity

acceptability, adequacy, adequateness, convenience, expedience, expediency, satisfactoriness, serviceableness, usefulness