(organic chemistry) an unsaturated aldehyde, CH₃CH=CH-CH=CH-CHO, used in the manufacture of perfumes etc

Alternative letter-case form of Catch-22

The decade that began on January 1, 2000 and ended on December 31, 2009. / The century that began on January 1, 2000 and ends on December 31, 2099.

the millennium bug

(Internet slang) Abbreviation of today, tomorrow, forever.

Abbreviation of twenty-four seven.

The decade of the 2020s. / The decade of the 1920s. / Temperatures from 20 to 29 degrees. / Ages between 20 and 29.

(Internet) The second generation of the World Wide Web, especially the movement away from static webpages to dynamic and shareable content, social networking, and online collaboration.

(physics) A radioactive isotope of polonium, ²¹⁰₈₄Po, having a half-life of 138 days; it as used as a reference alpha emitter in the calibration of radiation counters

(physics) A radioactive isotope of thorium, ²²⁸₉₀Th, having a half-life of 1.4 x 10¹⁰ years; it occurs naturally, and is a source of nuclear energy