Technical term in genetics referring to the linkage or coupling of genes. Compare 相反 (そうはん, repulsion).
See also: 相反
In genetics, coupling and repulsion are treated as opposing concepts.
In genetics, 相引 (coupling) is the opposite phase of linked genes from 相反 (repulsion).
Compound of 相 (mutual) and 引 (pull), likely a calque from English 'coupling' in genetics. The exact historical derivation is uncertain.