收缩 (shōu suō) is a verb meaning 'to contract' or 'to shrink', describing a physical reduction in size, volume, or area. The first character 收 (shōu) means 'to collect' or 'to draw in', while the second character 缩 (suō) means 'to shorten' or 'to pull back'. Together, they emphasize an inward, tightening motion—like muscles pulling together or blood vessels narrowing. This word is commonly used in medical, biological, and physical contexts, especially when discussing physiological processes such as muscle movement, blood flow regulation, or material behavior under temperature change.

It often appears in formal or technical language, though it’s also found in everyday descriptions of observable changes—e.g., skin tightening in cold weather or economic activity slowing down metaphorically. Unlike colloquial terms like 变小 (biàn xiǎo, 'to become smaller'), 收缩 implies active, often internal or automatic, reduction rather than passive diminishment. It frequently pairs with nouns like 血管 (blood vessels), 肌肉 (muscles), or 经济 (economy) to specify what is contracting.