actinium
ac·tin·i·um
noun \ak-ˈtin-ē-əm\Definition of ACTINIUM
: a radioactive trivalent metallic element that resembles lanthanum in chemical properties and that is found especially in pitchblende—symbol Ac; see element table
Test Your Vocabulary
Take Our 10-Question Quiz
|
|
|
Name That ThingTest Your Knowledge » |
|
True or False?A quick quiz about stuff worth knowing Take It Now » |
|
|
|
Join Us on FB & TwitterGet the Word of the Day and More Facebook | Twitter |
|
Get Our Free AppsVoice Search, Favorites, |
-
Learning English?
We can help.
Visit our free site designed especially for learners and teachers of English LearnersDictionary.com »
-
Bookstore: Digital and Print
Merriam-Webster references for Mobile, Kindle, print, and more. See all » -
Other Merriam-Webster Dictionaries
