plural of 540

(athletics) A long-distance running race over 5000 metres.

(physics) A minor stable isotope of iron, ⁵⁴₂₆Fe, having 26 protons and 28 neutrons; it amounts to about 6% of the element in nature

(physics) A minor stable isotope of iron, ⁵⁷₂₆Fe, having 26 protons and 31 neutrons; it amounts to about 2% of the element in nature

(physics) A minor stable isotope of iron, ⁵⁸₂₆Fe, having 26 protons and 32 neutrons; it amounts to about 0.3% of the element in nature

(Internet slang) Censored spelling of ass.

(physics) The major stable isotope of iron, ⁵⁶₂₆Fe, having 26 protons and 30 neutrons; it amounts to about 92% of the element in nature

(fandom slang) The fictional universe of DC Comics after the conclusion of Infinite Crisis, as shown in the 52 comic book series.

plural of 50-gon

(attributive) A six-channel surround sound audio system, having five full-bandwidth channels and one low-frequency effects channel.