from The American Heritage® Dictionary of the English Language, 5th Edition.

  • noun The haploid nucleus of a sperm or egg before fusion of the nuclei in fertilization.

from The Century Dictionary.

  • noun A primitive nucleus; the nucleus of an ovum or of a spermatozoön before these have united to form the definitive nucleus of an impregnated ovum.
  • noun In botany, the nucleus of a conjugating gamete, which on coalescing with another pronucleus forms the germ-nucleus.

from the GNU version of the Collaborative International Dictionary of English.

  • noun (Biol.) One of the two bodies or nuclei (called male and female pronuclei) which unite to form the first segmentation nucleus of an impregnated ovum.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

  • noun Either of the two haploid nuclei (of a sperm and ovum) that fuse during fertilization

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • noun the nucleus of the ovum or sperm after fertilization but before they fuse to form the nucleus of the zygote


Sorry, no etymologies found.



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  • "Having pierced the yolk, the spermatozoön loses its tail, while its head and connecting piece assume the form of a nucleus containing a cluster of chromosomes. This constitutes the male pronucleus, and associated with it there are a centriole and centrosome."

    - Henry Gray, 'Anatomy of the Human Body', 1918.

    September 20, 2009