【Decorous】 , 【decent】 , 【seemly】 , 【proper】 , 【nice】 apply to persons, their utterances, and their behavior, and mean conforming to an accepted standard of what is right or fitting or is regarded as good form.

Something is 【decorous】 when it is marked by observance of the proprieties; the term usually implies a dignified, sometimes ceremonious, sometimes prim, formality.

Something is 【decent】 (for other sense, see CHASTE) when it keeps within the bounds of what is appropriate or fitting to its kind or class, not only from the points of view of morality or social propriety but also from those of good taste or the exigencies of a situation.

Something is 【seemly】 when it is not only 【decorous】 or 【decent】 , but also pleasing to the eye, ear, or mind of the observer.

Something is 【proper】 when it is exactly what it should be according to accepted ethical or social standards or conventions.

Something is 【nice】 (see also 【NICE】 1 ; CORRECT) when it satisfies a somewhat fastidious taste in behavior, manners, or speech.