digraph

n two letters that represent a single sound (eg sh / F; F/, ea / i:; i/ in sheaf) 二合字母（代表一个单音的两个字母, 如sheaf中sh代表 /F; F/ , ea代表 /i:; i/）.

dig, dig down, dig in, dig out, dig up, digest, digestibility, digestible, digestion, digestive, digestive biscuit (also digestive), digestive system, digger, digging, digit, digital, dignified, dignify, dignitary, dignity, digress, digression, digressive, digs, dike, dike (also dyke), diktat, dilapidate, dilapidated, dilapidation, dilate, dilated, dilation, dilatorily, dilatoriness, dilatory, dilemma, dilettante, dilettantish, dilettantism,