• IPA: /ˈstɹɛŋ(k)θən/

strengthen (strengthens, present participle strengthening; past and past participle strengthened)

1. (transitive) To make strong or stronger; to add strength to; to increase the strength of; to fortify.

   strengthen a muscle

   strengthen a wall

   strengthen an army

   strengthen one's willpower

   strengthen one's 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 empower; to give moral strength to; to encourage; to enhearten.
   • 1769, The King James Bible, Book of 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.

• (to make strong or stronger) See also Thesaurus:strengthen
• (to augment) See also Thesaurus:augment

• weaken
• atrophy

• French: renforcer, affermir, raffermir, fortifier
• German: verstärken, stärken
• Italian: rinforzare, rafforzare, corroborare (rare)
• Portuguese: fortalecer, reforçar
• Russian: уси́ливать
• Spanish: fortalecer

• French: fortifier
• German: bestärken, stärken
• Italian: animare
• Spanish: animar

• German: verstärken

• Italian: rinforzarsi, rafforzarsi