SINCE 1828

An Encyclopædia Britannica Company

Medical Dictionary

radiopacity

play

noun ra·di·opac·i·ty \ ˌrād-ē-ō-ˈpas-ət-ē \

medical Definition of radiopacity

plural radiopacities

:the quality or state of being radiopaque

Seen and Heard

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

show

WORD OF THE DAY

legerity

play

alert quickness of mind or body

Words at Play

alt-59c52d6ee2f72

Breathing Life Into 'Inspire'

The word's origins are quite literal

alt-59c4207ecf106

Let's Talk 'Tea'

Spill it, sip it: just make it hot.

8 Words and Phrases from Boxing and Wrestling

Common terms that come from boxing and wrestling

alt-59c2960017c94

The Ambiguity of Pushing 'Up' and 'Back'

When you push a meeting, where does it go?

Ask the Editors

video-title-words-of-the-year-1066

Words of the Year: 1066

Or, Why Pig Meat is Called 'Pork' and Cow Meat is Called 'Beef'

How Often Is 'Biweekly'?

Don't get us started on 'bimonthly'

video-irregardless-grammar-peeve-blend-of-the-synonyms-irrespective-and-regardless

Irregardless

It is in fact a real word (but that doesn't mean you should use it).

video-moose-goose-weird-plurals

Weird Plurals

One goose, two geese. One moose, two... moose. What's up with that?

Word Games

young-plant-shoots

Merriam-Webster's New Words Quiz—Fall 2017 Edition!

You're going to have to memorize the dictionary again.

Take the quiz

stylized-drawing-of-woman-pole-vaulting-across-gap-to-get-trophy

Challenging Vocabulary Quiz Returns!

No tricks, just difficult words.

Take the quiz

Spell It

Can you spell these 10 commonly misspelled words?

Take the quiz

SCRABBLE® Sprint

SCRABBLE® Sprint

SCRABBLE® fans, sharpen your skills!

Play the game