The word proportionality may have one of a number of meanings:

• In mathematics, proportionality is a mathematical relation between two quantities.
• In law and politics, proportionality is a maxim in some theories of governance and a principle underpinning the constitution of the European Union.
• In politics, proportional representation is a democratic electoral system.
• In art, body proportions are the study of relation of human body parts to each other and the whole, essential for depiction of human figure.
• In typography, a proportional font is a font whose glyphs are displayed using varying widths.
• In the just war theory, proportionality is one of the conditions.