●含糊其辞的回答

也许吧。
Maybe. *虽然有可能性，但较接近于No, 概率只在40%左右，让人听上去是否定的语气。与perhaps同义。possibly更拘泥于形式，但同样含有消极的语感。probably的可能性较大，语感积极，概率在80%到90%左右，给对方以肯定的，即Yes的感觉。
Can you finish the report by Friday? (星期五之前你能写完那篇报告吗?)
Maybe. (也许吧。)
It may possibly rain, but it will probably be sunny again. (也许下雨，但可能过会儿又会晴了。)
Possibly.
Perhaps.
Probably.
不完全。
Not exactly. *“不能说完全是那样”、“不能断定就是那样”的意思。
Do you agree? (你同意吗?)
Not exactly. (不完全同意。)
Not quite.
可能是吧。
I guess so. *不能明确断定，“好像是”、“是吧”等推测的表达方式。
Don't you think Japanese people are healthier? (你不觉得日本人更健康些吗?)
I guess so. (可能是吧!)
I suppose so.
也许是真的吧。
It might be true. *听上去是不太肯定，接近于No (不)的感觉。
Do you think it's true? (你觉得那是真的吗?)
It might be true. (也许是真的吧。)
It's possible.
可能会吧。
It could be. *听对方说了许多之后，自己也觉得“可能会吧”时使用。
What do you think? (你觉得怎么样?)
It could be true. (也许吧!)
That could be.
That could be true.
我不太清楚。
I'm not sure. *没把握说时，或不知道时。
Is he in the office now? (他现在在办公室吗?)
I'm not sure. (我不太清楚。)
I'm not certain.
I can't say for sure.
但愿是这样。
I hope you're right.
It'll be sunny tomorrow. (明天是个好天吧。)
I hope you're right. (但愿是这样。)
有那么点儿。
Sort of.
Is your dog big? (你的狗大吗?)
Sort of. (说大也大吧!)
Kind of.
差不多吧!
It's something like that.
Is this it? (是这个吗?)
Yeah, it's something like that. (嗯，差不多吧。)
That's about it.
That'll do.
That's about right.
那得看情况。
It depends.
Don't you think you can save more money in Tokyo? (你不觉得在东京能攒更多的钱吗?)
It depends. (那得看情况。) *on a case by-case basis “基于具体情况”。
That depends.
也许是，也许不是。
Maybe yes, maybe no. *虽然有话要说，但又不想让对方明白时。
Are you going to ask him? (你打算去问他吗?)
Maybe yes, maybe no. (也许问，也许不问。)
但愿如此。
Hopefully. *表达虽然无法约定，但仍渴望能够实现的心情。
Can you play tomorrow? (明天能去比赛吗?)
Hopefully. (但愿能去。)
I hope so.
不能保证。
There's no guarantee. *带有也许不可能一切顺利的语感，但可以感觉到成功的概率很高。
Will it make money? (能挣大钱吗?)
There's no guarantee. (不能保证。)
I can't guarantee it.
我想是的。
I think so. *可以用于各种场合。表达“我想是的”、“是那样”的语感。
Will it rain today? (今天会下雨吗?)
I think so. (我想会吧。)
我说不好。
I can't say. *不愿意说出秘密或不足以提出意见时。
Do you know where they are? (你知道他们在哪儿吗?)
I can't say. (我说不好。)
I couldn't say.
I can't say for certain.
I can't say for sure.
I couldn't say for certain.
也是也不是。
Yes and no. *无法断定是“是”还是“不是”时。
Are the people friendly? (那些人都很友善吗?)
Yes and no. (也是也不是。)
Fifty-fifty. *俚语。
喜忧参半。/一半一半。
Half and half. *表示不能断言好还是不好，无法确定的心情。同时有向对方表示事情进展得不顺利、搁浅的语感。
Is that new plan effective? (那个新计划有效果吗?)
Half and half. (嗯，难说。)
我会试试。
I'll try. *“试试”、“努力”。
Can you find him? (你能找到他吗?)
I'll try. (我会试试。)
I'll do my best.
I'll try to.
怎么说呢。
It's difficult to say. *用于难以立刻回答时。
Is your boss nice to you? (你的老板对你好吗?)
It's difficult to say. (怎么说呢。)
It's hard to say.
还可以更好点。
Could be better. *考虑到对方的心情，避免给予对方否定的回答。“还有发展的余地”、“不能说是最好的”。
Is he a good salesman? (他是个很好的推销员吗?)
Could be better. (还可以更好点。)
他给我的回答很含糊。
He gave me an ambiguous answer. *ambiguous “可以有两种以上理解的，模棱两可的”。
His answer was very vague.
He wasn't very clear.

●保留意见

让我想想。
Let me think about it.
So, you should buy it now. (所以，你应该现在就买。)
Let me think about it. (让我想想。)
Give me time to think it over.
请给我点儿时间考虑。
I need some time to think it over.
I need more time to think about it.
我会考虑的。
I'll consider it. *正式的说法。表达不能马上回答时，有“请给我时间考虑”、“让我考虑考虑”的语感。
Do you like my idea? (你接受我的建议吗?)
I'll consider it. (我会考虑的。)
我考虑考虑吧。
I'll think about it. *比I'll consider it.的说法更随便，比直接拒绝语气要缓和。
Will you come to my party? (你来参加我的晚会吗?)
I'll think about it. (我考虑考虑吧。)
I'll sleep on it. *俚语。
I'll give it some thought.
我得琢磨琢磨。
I'll think it over.
Will you approve the proposal? (你同意我的计划吗?)
I'll think it over. (我得琢磨琢磨。)
请给我一个晚上的时间考虑。
Let me sleep on it.
Please give me a raise. (请给我涨工资。)
Let me sleep on it. (请给我一个晚上的时间考虑。)
我得研究研究。
I'll see what I can do.
We need longer breaks. (我们的休假有必要再长一些。)
I'll see what I can do. (我得研究研究。)