anneal

verb

an·​neal ə-ˈnēl 

annealed; annealing; anneals

transitive verb

1

a

: to heat and then cool (a material, such as steel or glass) usually for softening and making less brittle

Each bar, with its intricate twists, bevels and turns, had to be shaped individually. This shaping made some parts of the bars brittle … . To restore their flexibility, all the bars had to be annealed by heating, and then rapidly cooling them.

—Ivars Peterson

also : to cool slowly usually in a furnace

b

: to cause two complementary strands of nucleic acid (such as DNA or RNA) to join by hydrogen bonding

During repair of DNA double-strand breaks, cells must accurately anneal broken strands …

—Seiji N. Sugiman-Marangos et al.

also : to induce the binding of a genetic primer (see primer entry 2 sense 3) to a complementary single-stranded nucleic acid by slowly cooling single strands obtained from the heating and separation of double-stranded DNA or RNA

The primers are annealed to the single strands when the local temperature is reduced to between 50 and 65 C.

—Andrew J. DeMello

During PCR, fragments are heated so they will separate into single strands. A short nucleotide sequence called a primer is then annealed to each original template.

—George M. Church

2

: strengthen, toughen

intransitive verb

1

: to pair with a complementary strand of nucleic acid

A microRNA molecule can anneal to a messenger RNA (mRNA) containing a nucleotide sequence that complements the sequence of the microRNA …

—Carlo M. Croce

also : to bind to a complementary single-stranded nucleic acid during a process of heating and cooling

Site-specific primers, designed to complement the base pairs of the DNA region flanking the target, anneal to these regions.

—Norman Arnhelm and Corey H. Levenson

2

: strengthen, toughen

Mildred at least, is capable of love. In Veda, love has been annealed to a hard diamond of ambition.

—Stephen King

Did you know?

Anneal Has a Fiery History

If you were looking for a saying to apply to the word anneal, it might be "everything old is new again." The word was originally associated with one of the oldest technologies of humankind: fire. It derives from the Old English word onǣlan, which was formed from the Old English root āl, meaning "fire." In its earliest known uses, anneal meant simply "to set on fire." That sense has become obsolete, however, and nowadays anneal is associated with metalworking and glasswork as well as a much more recent technological development. As addressed in sense 3 of the definition, it has come to be used in the context of DNA research, in reference to the heating and cooling of double-stranded nucleic acid.

Examples of anneal in a Sentence

Recent Examples on the Web

Engineers sparingly tried annealing hardware space, so Juno's experience could be instructive for future missions. —Stephen Clark, ArsTechnica, 12 Sep. 2025

Some annealing quantum-type computers are already commercialized. —Chuck Brooks, Forbes.com, 1 Aug. 2025

They’re served in a heap in a bowl, the logs of potato annealed, shiny and splotched with balsamic vinegar. —Los Angeles Times, 7 July 2025

Workable quantum solutions that make use of annealing systems are now in use. —Chuck Brooks, Forbes, 22 Feb. 2025

In this instance, after annealing, nanoplastic molecules are physically bound together with the molecules of tetracycline. —Joe Salas, New Atlas, 3 Nov. 2024

Quantum annealing: This term is borrowed from annealing, a process that uses heat to alter the physical or chemical properties of a metal, glass, or plastic film to increase ductility and reduce hardness. —Ars Technica, 30 Oct. 2024

After annealing, the links are strong covalent bonds [below]. —IEEE Spectrum, 11 Aug. 2024

Word History

Etymology

Middle English anelen to set on fire, from Old English onǣlan, from on + ǣlan to set on fire, burn, from āl fire; akin to Old English ǣled fire, Old Norse eldr

First Known Use

1664, in the meaning defined at transitive sense 1a

Rhymes for anneal

• abele
• alkyl
• appeal
• cartwheel
• conceal
• congeal
• coquille
• corneal
• cornmeal
• flywheel
• foveal
• genteel

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Kids Definition

anneal

verb

an·​neal ə-ˈnē(ə)l 

: to heat and then cool so as to toughen and make less brittle

Medical Definition

anneal

transitive verb

an·​neal ə-ˈnē(ə)l 

1

: to heat and then cool (as steel or glass) usually for softening and making less brittle

2

: to heat and then cool (double-stranded nucleic acid) in order to separate strands and induce combination at lower temperatures especially with complementary strands

intransitive verb

: to be capable of combining with complementary nucleic acid by a process of heating and cooling

some bacterial nucleic acid anneals well with eukaryotic DNA