“Bertrand”

The following 2 entries include the term Bertrand.

Bertrand curve

noun

: either of two twisted curves having the property that the principal normals to one of them are also principal normals to the other

See the full definition

Bertrand lens

noun

: an auxiliary removable lens in the tube of a polarizing microscope used to obtain interference figures

See the full definition

Word of the Day

Listen to the pronunciation of cerulean

See Definitions and Examples »

Test Your Vocabulary

Name That Flower

  • any of a genus helianthus especially h annuus of new world composite plants with large yellow rayed flower heads bearing edible seeds that yield an edible oil
True or False

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

TAKE THE QUIZ
Play Blossom: Solve today's spelling word game by finding as many words as you can using just 7 letters. Longer words score more points.

Pick the best words!

PLAY
Love words? Need even more definitions?

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

Games & Quizzes

See All
Play Quordle: Guess all four words in a limited number of tries. Each of your guesses must be a real 5-letter word.
Quordle Can you solve 4 words at once?
Play Blossom: Solve today's spelling word game by finding as many words as you can using just 7 letters. Longer words score more points.
Blossom Word Game Pick the best words!
Play Missing Letter: a crossword with a twist. Each of the 25 puzzle words start with a different letter of the alphabet. Which letter is missing?
Missing Letter A daily crossword with a twist
tiny woman sitting on a pile of books reading
Little Words, Big Vocabulary Quiz Time to sweat the small stuff.