【Fit】 , 【suitable】 ,  【meet】 ,  【proper】 ,  【appropriate】 ,  【fitting】 ,  【apt】 ,  【happy】 ,  【felicitous】  are comparable when they mean right with respect to the nature, condition, circumstances, or use of the thing qualified.

Something is  【fit】 which is adapted or adaptable to the end in view, the use proposed, or the work to be done.

Sometimes, in addition,  【fit】 connotes competence or the possession of the required qualifications. Other times it suggests readiness (as in condition, state of health, mood, or inclination).

Something is  【suitable】 which answers the requirements or demands of the occasion, the circumstances, or the conditions or suggests no incongruity with them.

Something is  【meet】  which is not only 【suitable】 but nicely adapted to the particular situation, need, or circumstances; the word usually suggests rightness or justness rather than an absence of incongruity; thus, a punishment of a childish offense may be  【suitable】  if it is in accord with the years and mentality of the child, but it is not  【meet】 unless it suggests due proportion between the offense and its penalty.

Something is  【proper】  (see also DECOROUS ) which belongs to a thing on some justifiable grounds (as by nature, by custom, or by right reason). When, as often happens, fitness or suitability is stressed rather than natural or rightful association, 【proper】 then implies determination of fitness or suitability by logic, reasonableness, or good judgment.

Something is  【appropriate】  which is so eminently 【fit】 or 【suitable】 that it seems to belong peculiarly or distinctively to the person or thing with which it is associated, sometimes giving him or it a distinguishing grace or charm through its very congruity <an excitement in which we can discriminate two sorts of elements, the passions  【appropriate】  to the subject and the passion 【proper】 to the artist —Alexander >  <the eighteenth-century gentleman spoke with a refined accent, quoted the classics on  【appropriate】  occasions —Russell >  <we have agreed that our writing should be  【appropriate】  … that it should rise and fall with the subject, be grave where that is serious, where it is light not afraid of what Stevenson … calls "a little judicious levity" —Quiller-Couch >

Something is  【fitting】 which is in harmony with the spirit, the tone, the mood, or the purpose.

Something is  【apt】  (see also  【APT】 2 ); (see also QUICK 2 ) which is nicely fitted by its nature or construction to attain the end desired, to accomplish the purpose in view, or to achieve the results contemplated.

Something is  【happy】  (see also GLAD ), (see also LUCKY ) which is singularly 【appropriate】 and 【apt】 and therefore brilliantly successful or effective considered in its relation to the situation, the conditions, or other important factors.

Something is  【felicitous】 which is most opportunely, tellingly, or gracefully 【happy】 .