verb an·neal \ ə-ˈnēl \
Updated on: 3 Mar 2018

Definition of anneal

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 2primer 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
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

anneal was our Word of the Day on 11/27/2017. Hear the podcast!

Recent Examples of anneal from the Web

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.

anneal Has a Firey 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 onælan, which was formed from the Old English root āl, meaning "fire." In its earliest known uses, which date from around the year 1000, anneal meant simply "to set on fire." That sense has become obsolete, however, and nowadays anneal is associated with a much more recent technological development. It has come to be used in the context of DNA research, in reference to the heating and cooling of double-stranded nucleic acid.

Origin and Etymology of anneal

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

ANNEAL Defined for English Language Learners


Definition of anneal for English Language Learners

  • : to heat and then slowly cool (metal, glass, etc.) in order to make it stronger

ANNEAL Defined for Kids


verb an·neal \ ə-ˈnēl \

Definition of anneal for Students

annealed; annealing
: to heat (as glass or steel) and then cool so as to toughen and make less brittle

Medical Dictionary


transitive verb an·neal \ ə-ˈnē(ə)l \

medical Definition of anneal

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
: 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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