FIT, SUITABLE, MEET, PROPER, APPROPRIATE, FITTING, APT, HAPPY, FELICITOUS mean right with respect to some end, need, use, or circumstance.

FIT stresses adaptability and sometimes special readiness for use or action.

e.g. fit for battle

SUITABLE implies an answering to requirements or demands.

e.g. clothes suitable for camping

MEET suggests a just proportioning.

e.g. meet payment

PROPER suggests a suitability through essential nature or accordance with custom.

e.g. proper acknowledgement

APPROPRIATE implies eminent or distinctive fitness.

e.g. an appropriate gift

FITTING implies harmony of mood or tone.

e.g. a fitting end

APT connotes a fitness marked by nicety and discrimination.

e.g. apt quotations

HAPPY suggests what is effectively or successfully appropriate.

e.g. a happy choice of words

FELICITOUS suggests an aptness that is opportune, telling, or graceful.

e.g. a felicitous phrase

right or appropriate for a particular person, purpose, or situation:

«…に/…するのに» 適した, 適切な, ふさわしい «for, to/to do» (↔ unsuitable)

e.g. these toys are not suitable for children under five.

suitableness |ˈso͞odəbəlnəs| noun

late 16th century: from the verb suit, on the pattern of agreeable.