chief, head, leader

(physics) equilibrium length (length of a spring, etc. at rest)

centimetre

centimetre

nature / spontaneity

cubic centimeter (US), cubic centimetre (UK) - a unit of volume equal to that of a cube having sides each one centimeter in length, commonly used in fluid measure and for engine sizes. Symbols: cm³ and cc

natural / spontaneous

naturally / spontaneously / rarely / coincidentally

May

a unit of area (1cm × 1cm), symbol cm², (UK) square centimetre, (US) square centimeter.