mile·​stone | \ ˈmī(-ə)l-ˌstōn How to pronounce milestone (audio) \

Definition of milestone

1 : a stone serving as a milepost (see milepost sense 1)
2 : a significant point in development Graduating from college was an important milestone in her life.

Illustration of milestone

Illustration of milestone

milestone 1

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Examples of milestone in a Sentence

the new drug was regarded as a milestone in the treatment of heart disease
Recent Examples on the Web ABC News Live presents a pair of specials to mark the first 100 days of the most diverse Congress in history as the symbolic milestone approaches for President Joe Biden and his administration. Alisa Wiersema, ABC News, "Spotlight returns to police reform with little movement from White House: The Note," 13 Apr. 2021 In between the two milestone flights, the five space shuttles would deliver some of America’s greatest space triumphs and tragedies. Roger Simmons,, "Up, up and away: Space Shuttle Columbia first launched 40 years ago today," 12 Apr. 2021 Our first topic this Tuesday: the history of the 100-day milestone for U.S. presidents. CNN, "CNN 10 - April 13, 2021," 12 Apr. 2021 The brothers celebrate the milestone in the Renovation Issue of their magazine Drew + Jonathan Reveal. Glenn Garner,, "Property Brothers Surprised by Famous Friends and Past Homeowners to Mark 400th Renovation," 12 Apr. 2021 Now, in a hopeful milestone sure to cheer a pandemic-weary public, the first fish has followed its instincts back into the Milwaukee River. Paul A. Smith, Milwaukee Journal Sentinel, "Smith: Return of Milwaukee River sturgeon a hopeful milestone," 11 Apr. 2021 In some young polities such a milestone would be marked with fanfares. The Economist, "The Kurdish spring did not happen," 10 Apr. 2021 Carli Lloyd is close to an historic milestone as her next cap will be her 300th in a U.S. uniform. Mark Heim |, al, "FIFA’s USWNT-Sweden live stream (4/9): How to watch United States women’s national soccer team online," 10 Apr. 2021 Whenever the museum reaches a new milestone in followers, Hatch prints a newspaper announcement. Washington Post, "A printing press operator and a snail expert? These museum workers have become unlikely TikTok stars.," 10 Apr. 2021

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

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First Known Use of milestone

1662, in the meaning defined at sense 1

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Time Traveler for milestone

Time Traveler

The first known use of milestone was in 1662

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Statistics for milestone

Last Updated

16 Apr 2021

Cite this Entry

“Milestone.” Dictionary, Merriam-Webster, Accessed 17 Apr. 2021.

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More Definitions for milestone



English Language Learners Definition of milestone

: a stone by the side of a road that shows the distance in miles to a specified place
: an important point in the progress or development of something : a very important event or advance


mile·​stone | \ ˈmīl-ˌstōn How to pronounce milestone (audio) \

Kids Definition of milestone

1 : a stone by the side of a road showing the distance in miles to a given place
2 : an important point in progress or development His discovery was a major milestone in scientific research.

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