noun ·Rare ·Advanced level

Definitions

Noun

1. 1
   The transuranic chemical element with atomic number 93 and symbol Np. uncountable
2. 2
   a radioactive transuranic metallic element; found in trace amounts in uranium ores; a by-product of the production of plutonium wordnet

Synonyms

All synonyms

atomic number 93elementnpradioelementradiumsilver

Etymology

From Neptune + -ium, after the planet. The previous element is uranium, named after the previous planet: Uranus.

Related phrases

alpha-neptuniumbeta-neptuniumgamma-neptuniumatomic number

Data sourced from Wiktionary, WordNet, CMU, and other open linguistic databases. Updated March 2026.