In relativity physics, the shortening of an object along the direction of its motion relative to an observer. Dimensions in other directions are not contracted. This concept was proposed by the Irish physicist George F. FitzGerald (1851–1901) in 1889 and later independently developed by Hendrik Antoon Lorentz. Significant at speeds approaching that of light, the contraction results from the properties of space and time, not from compression, cooling, or any similar physical disturbance. Seealso time dilation.

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• Contraction (childbirth), a contraction during childbirth (basically referring to muscle contraction)
• Contraction (grammar), a word formed from two or more individual words.
• Syncope, the loss or reduction of sounds within a word.
• Braille contraction, used to decrease space and increase reading speed
• Economic contraction, a reversal of economic growth; the opposite of economic expansion.
• The reverse of thermal expansion
• Contraction mapping, in mathematics, a type of function on a metric space
• Edge contraction or vertex contraction, graph operations used in graph theory
• Muscle contraction, one that occurs when a muscle fiber lengthens or shortens
• Tensor contraction in tensor theory (in mathematics)
• Contraction, a stage in wound healing
• A structural rule in proof theory, see idempotency of entailment