noun
actinium
ak-TIN-ee-um
Actinium (noun) means a radioactive metallic chemical element with the symbol Ac and atomic number 89. Example: “Actinium is a radioactive element.”
noun
1
A radioactive metallic chemical element with the symbol Ac and atomic number 89.
"Actinium is a radioactive element."
"The chemical symbol for actinium is Ac."
"Actinium is found in uranium ores."
How to use actinium
Learner’s notesIn plain EnglishA radioactive metal, symbol Ac, atomic number 89.
When to use it
It is a scientific term, used mainly in chemistry and physics.
Memory tip
It is usually uncountable, so you normally use it without a or an.
Trace the full origin ↓
Common pairings
atomic number 89
a radioactive element
found in uranium ores
the symbol Ac
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_____ is a radioactive element.
Etymology
English borrowed it from French actinium, which is built from actin- plus the ending -ium.
Rhymes for actinium
See all rhymes for actinium →Frequently asked questions
What is actinium?
Actinium is a radioactive metallic chemical element with the symbol Ac and atomic number 89.
Where is actinium found?
It is found in uranium ores.
How do you pronounce actinium?
It is usually said ak-TIN-ee-um, with the stress on the second syllable.
What is the meaning of actinium?
"actinium" (noun) means a radioactive metallic chemical element with the symbol Ac and atomic number 89.
