SINCE 1828

An Encyclopædia Britannica Company

Medical Dictionary

pentatomic

adjective pen·ta·tom·ic \ ˌpent-ə-ˈtäm-ik \

medical Definition of pentatomic

1 : consisting of five atoms

2 : having five replaceable atoms or radicals

Seen and Heard

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

show

WORD OF THE DAY

cathexis

play

investment of mental or emotional energy

Words at Play

alt-5ade0f1ca7a0c

'Complement' vs. 'Compliment'

The distinction is clear (now).

Words from Letters in the Greek Alphabet

When English borrows from another alphabet

alt-5ada140ed3e28

'Preventive' or 'Preventative'?

alt-5ad8fc71357ed

Words We're Watching: 'Bluebeard,' the Verb

No, it's not a coiffure trend

Ask the Editors

2017 Word of the Year: Behind the Scenes

How we chose 'feminism'

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'

video-literally

Literally

How to use a word that (literally) drives some people nuts.

video-his-or-her

Is Singular 'They' a Better Choice?

The awkward case of 'his or her'

Word Games

Odd Habits and Quirks Quiz

Test your knowledge of strange human behaviors.

Take the quiz

cats-on-impossible-timber

More Confusing Words—Quiz

How many of these commonly confused words do you know?

Take the quiz

Name That Thing

Name That Thing

Test your visual vocabulary with our 10-question challenge!

Take the quiz

Citation

Do you know the person or title these quotes describe?

Play the game