frank : 强调毫无保留地畅所欲言，不受任何约束。
- a full and frank discussion
- There followed a frank exchange of views.
- The magazine, which gives frank advice about sex and romance, is aimed at the teenage market.
- To be perfectly frank with you, I don't think she's the person for the job.
open : 指不隐瞒自己的秘密，愿意向他人表露自己或公开暴露自己的缺点。
- There has been open hostility between them ever since they had that argument last summer.
plain : 指直言不讳，毫不做作或故弄玄虚。
- It's quite plain that they don't want to speak to us.
- The reason is perfectly plain.
- I made it quite plain (that) (= explained clearly that) I wasn't interested.
blunt : 指讲话坦白直率、不客气，但隐含不得体、不顾及他人感情等意味。
- I'll be blunt - that last piece of work you did was terrible.
honest : 指遵守正直等道德准则。
- She's completely honest.
- I'd like you to give me an honest answer/your honest opinion.
- He had an honest face (= he looked like he could be trusted).
- To be honest (with you), I don't think it will be possible.
sincere : 侧重指一个人出自内心地对某人某事表示一种诚意。
- a sincere apology
- He seems so sincere.
straightforward : 多用于答复、叙述等场合。指直截了当，不回避，或故弄玄虚。
- Roz is straightforward and lets you know what she's thinking.