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From rare Middle English strengthenen (14th c.), from earlier strengthen (12th c.), where -en is the infinitive ending. Probably the original form was reinterpreted as strength +‎ -en around the time when the infinitive ending was being apocopated in late Middle English.


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strengthen (third-person singular simple present strengthens, present participle strengthening, simple past and past participle strengthened)

  1. (transitive) To make strong or stronger; to add strength to; to increase the strength of; to fortify; to reinforce.
    to strengthen a limb, a bridge, an army;  to strengthen an obligation; to strengthen authority
    • c. 1600, William Shakespeare, Henry IV, Part 2
      Let noble Warwick, Cobham, and the rest, []
      With powerful policy strengthen themselves.
    • 1851, Anonymous, Arthur Hamilton, and His Dog
      A little hardship, and a little struggling with the rougher elements of life, will perchance but strengthen and increase his courage, and prepare him for the conflicts and struggles of after years.
  2. (transitive) To animate; to give moral strength to; to encourage; to fix in resolution; to hearten.
    • 1769, The King James Bible, Deuteronomy iii. 28
      Charge Joshua, and encourage him, and strengthen him.
    • 1910, Emerson Hough, chapter I, in The Purchase Price: Or The Cause of Compromise, Indianapolis, Ind.: The Bobbs-Merrill Company, OCLC 639762314, page 0124:
      "A fine man, that Dunwody, yonder," commented the young captain, as they parted, and as he turned to his prisoner. "We'll see him on in Washington some day. He is strengthening his forces now against Mr. Benton out there. []."
  3. (transitive) To augment; to improve; to intensify.
  4. (intransitive) To grow strong or stronger.



Derived termsEdit