diffident
词根词缀：
difficult adj. 困难的
dif 不，否定 + fic 做 + ult → 不好做 → 困难的
diffident adj. 自卑的
dif 不，否定 + fid 相信 + ent 关于…的 → 不相信〔自己〕的 → 自卑的
differ v. 不同
dif 分开 + fer 带来 → 分开带来 → 不同
difference n. 不同
differ的名词
diffluence n. 分流；溶解
dif 分开 + flu 流 + ence 表状态 → 分开流 → 分流
diffuse v. 撒播
dif 分开 + fus 流 + e → 使散开流 → 撒播
数据来源：新东方英语词汇速记大全
相关例句：
He was a little diffident, but quite self-possessed.
他有点信心不足，但很镇静。
Japanese officials have been more diffident about the agreement and insist their country's sanctions remain in place.
日本官方对朝鲜的态度信心不足，坚称将继续对其制裁。
He looked diffident, and amiable, and independent, and he, too, was evidently english.
他显得忸怩羞怯，又和蔼又任性，显然他也是一个英国人。
His fault is that he's too diffident.
他的过失是太缺乏自信啦。
If students do not wear the same uniforms, students wearing cheap clothes may have the feeling of self-contempt and be diffident about expressing one's opinions in class.
如果学生不穿统一的校服，穿廉价衣服的学生可能会有自卑情绪，在课堂上怯于表述自己的意见。
He suddenly felt diffident in the presence of these people.
当着大家的面，他突然感到心里发虚。