time dilation


Definition of time dilation

: a slowing of time in accordance with the theory of relativity that occurs in a system in motion relative to an outside observer and that becomes apparent especially as the speed of the system approaches that of light

called also time dilatation

Examples of time dilation in a Sentence

Recent Examples on the Web

There is a phenomenon of relativity known as time dilation, in which time appears to slow down almost to a stop for bodies that approach the speed of light. Jerry Adler, Newsweek, "Stephen Hawking, Master of the Universe: Our 1988 Cover Story on the Legendary Physicist," 14 Mar. 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'time dilation.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

First Known Use of time dilation

1934, in the meaning defined above

Keep scrolling for more

Learn More about time dilation

Statistics for time dilation

Look-up Popularity

Time Traveler for time dilation

The first known use of time dilation was in 1934

See more words from the same year

More from Merriam-Webster on time dilation

Britannica.com: Encyclopedia article about time dilation

Comments on time dilation

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


showing courage and determination

Get Word of the Day daily email!

Test Your Vocabulary

Words for Summer: A Quiz

  • a closeup of a sunflower
  • Which of the following words means “of or relating to summer”?
How Strong Is Your Vocabulary?

Test your vocabulary with our 10-question quiz!


Test Your Knowledge - and learn some interesting things along the way.

Love words? Need even more definitions?

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