certainly ['sɝtnli] 词频1 词根: cert

adv. 无疑;当然;确定;肯定;

💡 certain确实的+ly副词后缀，…地 → 确实地，一定地，当然地

"I shall certainly keep a beady eye on his behaviour."

近义：indeed, indubitably, inevitably, infallibly, assuredly, absolutely 反义：hesitatingly, hesitatively, indecisively, arguably, tentatively, wonderingly

remain [rɪ'men] 词频1 词根: man

n. 剩余物，残骸;残余;遗迹;遗体; vi. 留下;保持;留待;依然; vi.& link-v. 搁置;剩余，剩下;逗留;终属，归于;

💡 re回+main逗留→回来留下→剩余

"The money was donated by a local businessman who wishes to remain anonymous ."

近义：keep, stay, get, persevere, hold, continue 反义：vary, alter

single ['sɪŋɡl] 词频1

adj. 单一的;（打斗、比赛等）一对一的;惟一的;适于一人的; n. 单程票;（旅馆等的）单人房间;[复数]（高尔夫球一对一的）二人对抗赛;[常用复数][美国、加拿大英语]未婚（或单身）男子（或女子）; vt. 挑选; vi. 作一垒手;

💡 sing(唱歌)+le(乐):唱乐- 单身汉 网友：马 胜 敏 补充：1：：练习这首歌（sing）时，单个的人是无法练习的，只有两个人配合好了（le）才能唱出效

"She had a brainstorm in the exam and didn't answer a single question."

近义：individualize, personalise, personalize, singularize, distinguish, bachelor 反义：manifold, multiplex, wedded