“planck's”

We have one entry that includes the term planck's.

Planck's constant

noun

: a constant that gives the unvarying ratio of the energy of a quantum of radiation to its frequency and that has an exact value of 6.62607015 × 10−34 joule seconds —symbol h

See the full definition

Word of the Day

Listen to the pronunciation of dog days

See Definitions and Examples »

Test Your Vocabulary

Which Came First?

  • baby chick with a brown egg
  • hot take or cold shoulder?
How Strong Is Your Vocabulary?

Test your vocabulary with our 10-question quiz!

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 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?
The Missing Letter A daily crossword with a twist
thumbnail graphic with text word of the day quiz
Weekly "Word of the Day" Quiz See how well you know each Word of the Day for Ju...
See All