The decade from 2030 to 2039.

(mobile telephony) Retronym referring to standards before 2.75G.

(computing) An issue for computing and data storage situations in which time values are stored or calculated as a signed 32-bit integer, and this number is interpreted as the number of seconds since 00:00:00 UTC on 1 January 1970. Such implementations cannot encode times after 03:14:07 UTC on 19 January 2038

(code word, euphemistic) Casualties for transportation in the Soviet and modern Russian military. In official use, cargo 200 refers to bodies contained in zinc-lined coffins, but in a military context it may be used for dead bodies as they are transported from the battlefield.

(idiomatic) In hindsight things are obvious that were not obvious from the outset; one is able to evaluate past choices more clearly than at the time of the choice.

(physics) The major stable isotope of neon, ²⁰₁₀Ne, having ten protons and ten neutrons; it amounts to over 90% of the element in nature

(physics) A rare stable isotope of neon, ²¹₁₀Ne, having ten protons and eleven neutrons; it amounts to less than 0.3% of the element in nature