(medicine) Initialism of optical coherence tomography: an optical signal acquisition and processing method that captures high-resolution three-dimensional images from biological tissues.

Form of octa- or octo- used before a vowel.

Alternative spelling of Oct.

Abbreviation of October.

(computing, informal) Abbreviation of octal.

Initialism of One Country, Two Systems, the political structure by which Hong Kong and Macau are administered separately from mainland China. Chinese: 一國兩制／一国两制 (yī guó liǎng zhì).

eight

(chemistry, of an acid) containing eight replaceable hydrogen atoms / (chemistry, of a salt) having eight atoms of a univalent metal

(meteorology) The proportion of the sky that is obscured by clouds, in eighths (one octa means that one eighth of the sky is obscured, two octas that one quarter is obscured, and so on).

(organic chemistry) Any of very many isomers of the aliphatic hydrocarbon having 28 carbon atoms, but especially n-octacosane CH₃(CH₂)₂₆CH₃