noun, plural: zygotes
A cell in diploid state following fertilization or union of haploid male sex cell (e.g. sperm) and haploid female sex cell (e.g. ovum).
To be precise, zygote is the term used to refer to the cell as a result of the fusion of two haploid nuclei during fertilization until the first cleavage. When the zygote starts to divide and multiply, it is called an embryo.
Word origin: from Greek zugōtos ‘joined’, from zugoun ‘to join’.
Related forms: zygotic (adjective).
See also: copula, zygogenesis, monozygotic twins, heterozygosity, homozygous.