Proper may refer to:

• Proper (liturgy), the part of a Christian liturgy that is specific to the date within the Liturgical Year
• Proper frame, such system of reference in which object is stationary (non moving), sometimes also called a co-moving frame

In mathematics:

• Proper map, in topology or algebraic geometry, a property of continuous function between topological spaces, if inverse images of compact subsets are compact
• Proper transfer function, a transfer function in control theory in which the degree of the numerator does not exceed the degree of the denominator
• it is also used to indicate a subspace or a subset is strictly smaller than its parent