noun ·Uncommon ·Advanced level

Definitions

Noun

1. 1
   A radioactive, metallic chemical element (symbol: Ac) with an atomic number of 89; found in uranium ores. uncountable, usually
2. 2
   a radioactive element of the actinide series; found in uranium ores wordnet

Synonyms

All synonyms

acatomic number 89

Example

More examples

"Actinium is a radioactive element."

Etymology

Borrowed from French actinium. actin- + -ium.

Related phrases

actinium Aactinium Bactinium Cactinium emanationactinium fluorideactinium seriesactinium-Keka-actiniumatomic number

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