- digraph (n.)
[digraph 词源字典]
- 1788, in linguistics, from Greek di- "twice" (see di- (1)) + -graph "something written," from Greek graphe "writing," from graphein "to write, express by written characters," earlier "to draw, represent by lines drawn" (see -graphy). In mathematics, from 1955, a contraction of directed graph.[digraph etymology, digraph origin, 英语词源]