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• harden
  harden

  verb (used with object)

  to make hard or harder.
• Harden
  Harden

  noun

  Sir Arthur, 1865–1940, English biochemist: Nobel Prize 1929.

harden

¹ American  

[hahr-dn] / ˈhɑr dn /

verb (used with object)

hardens, present (3rd person singular) hardened, past participle, past hardening present participle

1. to make hard or harder.

   to harden steel.

   Synonyms:

   ossify, petrify, indurate, solidify

   Antonyms:

   soften

2. to make pitiless or unfeeling.

   to harden one's heart.

3. to make rigid or unyielding; stiffen.

   The rigors of poverty hardened his personality.

4. to strengthen or confirm, especially with reference to character, intentions, feelings, etc.; reinforce.

   Synonyms:

   nerve, brace, steel, fortify

   Antonyms:

   weaken

5. to make hardy, robust, or capable of endurance; toughen.

6. Military. to reinforce the structure of (a military or strategic installation) to protect it from nuclear bombardment.

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verb (used without object)

hardens, present (3rd person singular) hardened, past participle, past hardening present participle

1. to become hard or harder.

2. to become pitiless or unfeeling.

3. to become rigid or unyielding; stiffen.

   His personality hardened over the years.

4. to become confirmed or strengthened.

   His resistance hardened.

5. to become inured or toughened.

   The troops hardened under constant fire.

6. Commerce. (of a market, prices, etc.)

   1. to cease to fluctuate; firm.

      When the speculators withdrew from the market, the prices hardened.

   2. to rise higher.

Harden ² American  

[hahr-dn] / ˈhɑr dn /

noun

1. Sir Arthur, 1865–1940, English biochemist: Nobel Prize 1929.

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harden ¹ British  

/ ˈhɑːdən /

verb

1. to make or become hard or harder; freeze, stiffen, or set

2. to make or become more hardy, tough, or unfeeling

3. to make or become stronger or firmer

   they hardened defences

4. to make or become more resolute or set

   hardened in his resolve

5. (intr) commerce

   1. (of prices, a market, etc) to cease to fluctuate

   2. (of price) to rise higher

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harden ² British  

/ ˈhɑːdən /

noun

1. a rough fabric made from hards

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Other Word Forms

Derived Forms

• hardenability
  noun
• overharden
  verb
• reharden
  verb
• hardenable
  adjective
• unhardenable
  adjective

Inflected Forms

Participles

• hardening
  present
• hardened
  past

Conjugated Forms

Present

• harden
  simple
• hardens
  simple
• have hardened
  perfect
• has hardened
  perfect
• am hardening
  progressive
• are hardening
  progressive
• is hardening
  progressive
• have been hardening
  perfect progressive
• has been hardening
  perfect progressive

Past

• hardened
  simple
• had hardened
  perfect
• was hardening
  progressive
• were hardening
  progressive
• had been hardening
  perfect progressive

Future

• will harden
  simple
• will have hardened
  perfect
• will be hardening
  progressive
• will have been hardening
  perfect progressive

Etymology

Origin of harden

Middle English word dating back to 1150–1200; see origin at hard, -en ¹

Example Sentences

The impact of this, he said, is Israeli troops "having to move more cautiously, harden positions, use physical protective measures such as nets and cages, and devote more attention to immediate local defence".

From BBC • May 16, 2026

Inflation will test him almost immediately, and numbers well above the Fed’s target could force the committee to harden its language faster than he would prefer, narrowing his room to maneuver.

From Barron's • May 6, 2026

“The lesson that can be taken away is just thinking about how to harden and strengthen security at future events when you have so many high-profile people,” she said.

From Los Angeles Times • Apr. 26, 2026

The service takes technical measures to harden the security of its server network.

From Salon • Mar. 13, 2026

“You must start to harden yourself. I’ll show you. It won’t be easy. You must want it.”

From "Son" by Lois Lowry