I. ˈn(y)üklēˌän noun
( -s )
Etymology: International Scientific Vocabulary nucle- + -on
: a proton or neutron especially in the atomic nucleus
• nu·cle·on·ic | ̷ ̷ ̷ ̷|änik adjective
II. noun
: a hypothetical single entity with one-half unit of isospin capable of manifesting itself as either a proton or a neutron and of making transitions between these two states