(mathematics) Synonym of pentacontagon: A 50-sided polygon.

(Canada, US, fiction) Pertaining to a fake telephone number. The local exchange and area code number 555 was reserved in North American dialing plan for fictional numbers, prior to the 21st century.

(physics) A minor stable isotope of titanium, ⁵⁰₂₂Ti, having twenty-two protons and twenty-eight neutrons; it amounts to about 5% of the element in nature

(physics) The only stable isotope of vanadium, ⁵¹₂₃V, having twenty-three protons and twenty-eight neutrons