plural of optical activity

plural of extravehicular activity

plural of displacement activity

(grammar, uncountable) the form in which the subject of a verb carries out some action / (grammar, countable) a form in a particular language used to express the active voice

(astronomy) A galaxy where a significant fraction of the energy output is not emitted by the normal components of a galaxy.

(physics) a property caused by asymmetrical molecular or crystal structure that enables a compound or crystal to rotate the plane of incident polarized light

(chemistry, of a crystal or compound) Exhibiting optical activity.

capable of lowering the surface tension of a liquid

Any activity done by an astronaut outside of a spacecraft etc; a spacewalk or moonwalk.

(law, often derogatory) The act of replacing an impartial interpretation of existing law with the judge's personal feelings about what the law should be.