I am not quite sure whether I am free.

I am not sure.

It depends.

Maybe. Maybe not.

It looks as if I am not free tonight.

I am not free at all.

I am just remember that I have got another appointment.

Sorry .I am afraid I can not go to the theatre tonight.

I am away tonight.

Sorry I can not .I have got a terrible toothache now.

I am really a little bit busy for the next few weeks.

I will give you a ring one of these days .

I would love to ,but I am afraid I will be quite busy then.

I will come round to other place.

I am afraid I am busy on Sunday.

It might be a little early.

That is difficult for me.

I have to visit  a friend tonight.

Thanks for the offer, but I am afraid I have an essay to finish.

It is very kind of you to invite ,but I am afraid I am busy tonight.

Well , tonight is not really convenient .How about next Friday?

I would love to , but I do not suppose I have time.

It is very nice of you to ask, but honestly, I really would not be able to.

It is very kind of you to invite me, but I have got a previous engagement.

I would love to go ,but I do not think my husband will make it as he's schedule d to leave for a conference the day before the occasion.

I regret we are unable to accept your kind invitation.

You know I could not possibly make it as I will be away on a business trip in New York.

You know I have already been asked to join my family for the weekend.

It is unlike we will be back before the day you suggested .In view of this ,we are unable to accept your invitation.

谢绝

我不能肯定是否有空。

我不能肯定。

看情况而定。

也许行，也许不行。

看来今晚没空。

我一点时间都没有。

我刚想起来我另外有个约会。

对不起，今晚恐怕不能去剧院了。

今晚我要出门。

我现在牙疼的历害，去不了。

下几个礼拜我都比较忙。

这几天我会给你打电话的。

那真不错，不过估计那会我会比较忙。

我要去别的地方。

恐怕星期天我没空。

时间可能早了点了。

有点困难。

我今晚要去看个朋友。

谢谢你的盛情，但是我有篇稿子必须完成。

谢谢你的邀请，但是我今晚很忙。

今晚不太方便，下星期五怎么样？

我很想去，可惜没有时间。

谢谢你的邀清，但是说实话，我确实去不了。

谢谢你的盛情邀请，但我早已有约会。

我很想去，不过我先生可能去不了。宴会前一天他已定好去参加一个会议。

很遗憾不能接受你的盛情邀请。

你知道，那天我实在去不了，因为我得去纽约出差。

你知道我家人已邀我一起度周末了。

你定的那个日子我们可能回不来，所以无法接受你的邀请了