- suitable, appropriate, or correct, as in 'The proper person to consult about the desirability of an operation is your doctor' or 'The young girl was not a proper person to be left in charge of a six-month old baby'.
- morally correct, upright, as in He's a very proper person: I'm sure he wouldn't be guilty of any financial irregularity'. Sometimes the word has a negative significance, implying that the person is too strict in their application of moral principles or too concerned with appearances, and so insufficiently flexible, humane, or sympathetic, as in 'He's a very proper person: I don't think he'll look sympathetically on your request'.
- genuine, up to the appropriate standard, as in 'I don't consider toast and coffee a proper breakfast'.
In British English 'proper' may be used in informal speech with much the same meaning as 'real' as an intensifier, as in 'He made a proper fool of himself in front of all the distinguished guests' or 'You've got us into a proper mess'. In some English dialects 'proper' is used as an adverb with much the same meaning as 'really' or 'very', as in 'Our teacher is proper clever'. In academic writing you should never use 'proper' in this way as an intensifier.
'Proper', used prenominally, occurs in a number of technical expressions:
- In grammar a proper name or proper noun is the name of a person, place, or institution - e.g., John, Newcastle, or the United Nations. In English such words are always written with a capital letter.
- In mathematics a proper fraction is a fraction that is less than one, i.e., the numerator is less than the denominator, e.g., 1/4 or 17/18.
- In mathematics and logic a proper subset is a set which contains some but not all of the members of the set of which it is a subset, e.g., the set of all even numbers from 0 to 100 is a proper subset of the set of all numbers from 0 to 100. (The expression 'proper subset' is necessary in view of the logicians' dictum that every set is a subset of itself.)
- according to the precise meaning (of the preceding word) (in contrast to what might be meant by the word on a looser interpretation), or the essential, central, or main part (of what is denoted by the preceding word), as in 'The city proper is on the north bank of the river, on the south bank there is only an industrial estate' or 'It took us two days to reach Florence, and then our holiday proper began'.
- belonging to or characteristic of a thing, as in 'You should treat him with the respect proper to his status' or 'He has been given a salary proper to the level of his responsibilities in the company'.
The word 'proper' is used as a noun in the phrase 'the proper of the Mass', i.e., those parts of the Mass which change according to the day on which the Mass is being celebrated - by contrast with 'the ordinary of the Mass', i.e., those parts of the Mass which remain unchanged throughout the ecclesiastical year.
- Etymological note: the word 'proper' comes, through French, from the Latin adjective proprius, which means: one's own, peculiar, personal, characteristic, or (used of words) literal or regular. In French, too, the adjective propre has different meanings depending on its position. Prenominally it has the general meaning of '(one's) own, (the very) same' (notre propre maison ~ 'our own house' or tes propres paroles ~ 'your very words'); postnominally it means 'clean', as in une maison propre - 'a clean house' or j'ai les mains propres - 'my hands are clean'.