Main Entry: nu·cle·on

Pronunciation: \ˈnü-klē-ˌän, ˈnyü-\

Function: noun

Etymology: International Scientific Vocabulary

Date: 1923

1 : a proton or neutron especially in the atomic nucleus
2 : a hypothetical single entity with one-half unit of isospin that can manifest itself as either a proton or a neutron

— nu·cle·on·ic \ˌnü-klē-ˈä-nik, ˌnyü-\ adjective