an·​neal ə-ˈnēl How to pronounce anneal (audio)
annealed; annealing; anneals

transitive verb

: 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
: 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

intransitive verb

: 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
: 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.

Example Sentences

Recent Examples on the Web Together, hundreds of them can anneal into a solid block. Ed Yong, Discover Magazine, 29 Nov. 2012 For hybrid algorithms, the back and forth between classical and annealing worlds means regular communications with the D-Wave hardware, which helped motivate the company to try to reduce the latency of those communications. John Timmer, Ars Technica, 1 Oct. 2019 Further Reading D-Wave announces the next generation of its quantum annealer The other challenge annealing faces is that classical algorithms are constantly improving. John Timmer, Ars Technica, 1 Oct. 2019 Solutions are downhill One way to compute a solution to a problem is called annealing. Chris Lee, Ars Technica, 13 June 2019 The slow cooling of the glass allows it to anneal, relieving internal stresses and improving durability. Jay Bennett, Popular Mechanics, 14 Feb. 2018 Before and after the Eagles’ organized team activities last spring, Nelson Agholor retreated to his hometown for a series of training sessions with an old friend and mentor that would anneal his mind as much as his body. Mike Sielski,, 8 Oct. 2017 To make the object, the copper was alternately hammered and annealed—a process of heating metal and allowing it to cool slowly. Brigit Katz, Smithsonian, 12 June 2017 See More

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'anneal.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

Word History


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

Time Traveler
The first known use of anneal was in 1664


Dictionary Entries Near anneal

Cite this Entry

“Anneal.” Dictionary, Merriam-Webster, Accessed 8 Feb. 2023.

Kids Definition


an·​neal ə-ˈnē(ə)l How to pronounce anneal (audio)
: to heat and then cool so as to toughen and make less brittle

Medical Definition


transitive verb
an·​neal ə-ˈnē(ə)l How to pronounce anneal (audio)
: to heat and then cool (as steel or glass) usually for softening and making less brittle
: 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

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