1

actinoid

adjective ac·ti·noid \ ˈak-tə-ˌnȯid \

Definition of actinoid

1 : resembling a ray especially of a radially symmetrical animal
2 : exhibiting radial symmetry

There's more!

Love words? You must — there are over 200,000 words in our free online dictionary, but you are looking for one that’s only in the Merriam-Webster Unabridged Dictionary.

Start your free trial today and get unlimited access to America's largest dictionary, with:

  • More than 250,000 words that aren't in our free dictionary
  • Expanded definitions, etymologies, and usage notes
  • Advanced search features
  • Ad free!
Already a subscriber? Log in.

Origin and Etymology of actinoid

actin(ia) +2-oid (probably after actinoida or actinoidea )


2

actinoid

noun ac·ti·noid \ ˈak-tə-ˌnȯid \

Definition of actinoid

plural actinoids
chemistry
: actinide
  • The actinoid elements (or actinides; An) constitute a series of 14 elements which are formed by the progressive filling of the 5f electron shell and follow actinium in the periodic table (atomic numbers 90-103).
  • —Mirtat BouroushianElectrochemistry of Metal Chalcogenides2010

Origin and Etymology of actinoid

actin(ide) +1-oid


Seen and Heard

What made you want to look up actinoid? Please tell us where you read or heard it (including the quote, if possible).

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!

WORD OF THE DAY

to make fruitful or productive

Get Word of the Day daily email!

Test Your Vocabulary

Star Wars Words Quiz

  • cu-jedi-training
  • The bounty portion of bounty hunters (such as Boba Fett) comes from a Latin word meaning
True or False

Test your knowledge - and maybe learn something along the way.

TAKE THE QUIZ
SCRABBLE® Sprint

Test Your Knowledge - and learn some interesting things along the way.

TAKE THE QUIZ

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!