Try Our Apps
World Series Quiz
the time required for a collection of atoms of a particular radionuclide to decay to a fraction of the initial number equal to 1/e, where e = 2.7182818 …, used as the base of natural logarithms.
Based on the Random House Dictionary, © Random House, Inc. 2016.
Cite This Source
Discover our greatest slideshows
8 Offbeat Literary Genres to Get...
Decode the pieces of our favorite...
Know These 9 Commonly Confused...
Uncover the mysteries of the marks...
Browse more topics on our blog
What Is the Difference Between Discreet and Discrete?
Learn the correct uses of these two commonly confused homophones.
What Character Was Removed from the Alphabet?
What mistaken pronunciation gave this character its name?
This small mark has two primary uses: to signify possession or omitted letters.
How Do I Get a Word into the Dictionary?
People invent new words all the time, but which ones actually make it?
Word of the Day
Difficulty index for
Few English speakers likely know this word
Word Value for
Words With Friends
Nearby words for decay time