before vowels hom-, word-forming element meaning "same, the same, equal, like" (opposed to hetero-), from Greek homos "one and the same," also "belonging to two or more jointly" (from PIE *somo-, from root *sem- (1) "one; as one, together with").
1880, coined 1878 by German cytologist Eduard Strasburger (1844-1912), the widespread attribution to William Bateson being apparently erroneous; from Greek zygotos "yoked," from zygon "yoke" (from PIE root *yeug- "to join").
word-forming element making adjectives from nouns, meaning "having, full of, having to do with, doing, inclined to," from Old French -ous, -eux, from Latin -osus (compare -ose (1)). In chemistry, "having a lower valence than forms expressed in -ic."
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Harper, D. (n.d.). Etymology of homozygous. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/homozygous