New words：

basis [ˈbeɪsɪs] n.基础；原因；要素；

Sample Sentences：

The basis of a good marriage is trust.
The basis of this drink is orange juice.
Nothing can shake the basis for my belief.

belief [bɪˈlif] n.信仰；信念；相信；信心

New words：

topic [ˈtɒpɪk] n. 话题；题目；标题

Sample Sentences：

We'd like to see your opinion on this topic.
The topic of the writing competition is "My Teacher".
I just looked at the topic for my speech about thirty seconds ago before I walked in the door.

New words：

regretful [rɪˈɡretf(ə)l] adj. 后悔的；失望的；令人惋惜的；遗憾的

Sample Sentences：

I'm regretful that I made such a mistake.
I am never regretful to choose the major by now.
You can see from his face that he is regretful now.

New words：

regret doing 后悔做了；对做过的事表示遗憾、后悔
regret to do 后悔去做；对将要做的事表示遗憾

Sample Sentences：

There are many things I regret doing to you.
I regret to tell you that I can't spend the weekend with you.

New words：

regret [rɪˈɡret]
n.遗憾；懊悔；痛惜；失望
v.懊悔；感到遗憾；惋惜

Sample Sentences：

She looked back on the past without regret.
She has not shown any real regret for what she did.

I deeply regret what I said.
I regret that I am unable to accept your kind invitation.