What does harden mean?
Harden means to make something hard or to become hard and firm. It is especially common in technical contexts, such as describing the treatment of metal, plastics, concrete, or other materials to increase strength or resistance. Figuratively, harden describes a person becoming tougher, more determined, or less affected by hardship and emotional pain. It can also mean to prepare someone to resist temptation, influence, or other risks. The word is useful because it combines a straightforward physical meaning with a broad figurative sense: just as a material can be made tougher, a person can acquire resilience or emotional distance. The expression “harden into” suggests a gradual transformation, while “harden against” emphasizes preparation for resistance.
To make or become hard, firm, or resistant; to become tough or less sensitive.
"The heat gradually hardened the clay into a solid shape."
The verb may take an object, as in “harden the steel,” or be used without an object, as in “her resolve hardened.”
Obsolete or regional: hard or tough.
"The harden ground made travel difficult."
This adjective sense is rare and is mainly preserved in older or regional usage.
To harden something is to strengthen its resistance; to harden a person is to make them less easily hurt by the world.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does harden come from?
The English word appears in Middle English, having come through Old French from Latin durus, meaning “hard.” In its earliest uses, harden referred to making a substance physically hard or firm. Its relatives, including durable, endure, and duration, reflect the same Latin root and its associated ideas of strength, firmness, and lasting through time.
Related word forms
How harden is actually used
The verb can be transitive or intransitive: something hardens, or a person or process hardens something. Its figurative uses often carry a slightly negative or emotionally distant connotation, especially when describing a person becoming less sensitive. In technical contexts, the word is usually neutral and refers to a deliberate physical or chemical change.