cte·nid·i·um | \ -ēəm \
plural ctenidia\ -ēə \
Definition of ctenidium
1 : the gill of a mollusk consisting typically of a respiratory structure that resembles a comb or feather, has a main stem with lateral lamellae, and is developed from the inner side of the mantle
—distinguished from ceras
2 : a structure consisting of a row of spines resembling the teeth of a comb on the head or thorax, or both, of certain fleas
Keep scrolling for more
Test Your Vocabulary
Slippery Words Quiz—Changing with the Times
- What is an earlier meaning of nice?

Can you spell these 10 commonly misspelled words?
TAKE THE QUIZ
Anagram puzzles meet word search.
TAKE THE QUIZLove words? Need even more definitions?
Merriam-Webster unabridgedWords at Play
Ask the Editors
Word Games
Slippery Words Quiz—Changing with the Times
Do you know these earlier meanings of words?
Take the quizWords of Snow and Ice Quiz
A selection of words from the chillier parts of t...
Take the quizSpell It
Can you spell these 10 commonly misspelled words?
Take the quizSCRABBLE® Sprint
SCRABBLE® fans, sharpen your skills!
Play the game
Share ctenidium