agree with / agree to / agree on
1. agree with
(1) 表示同意某人或某人的意见、想法、分析、解释等 (即持同一观点)。如：
I quite agree with you. 我完全同意你的意见。
We agree with what you say. 我们同意你说的。
(2) 表示“(食物、天气、工作等)对……适宜”。如：
The food does not agree with me. 这食物对我不适合。
Hard work does not agree with him. 艰苦的工作对他不适宜。
(3) 表示“与……一致”。如：
His story agrees with the facts. 他的陈述与事实相符。
A verb must agree with its subject in person and number. 动词必须和它的主语在人称和数方面保持一致。
2. agree to
(1) 后接某些名词，表示同意或接受某事，尤其指别人提出的某事，有时可能是自己不喜欢的事。
He agree the plan (the date). 他同意了这个计划(日期)。
We agreed to their arrangement. 我们同意了他们的安排。
I was forced to agree to it, but at heart I didn’t quite agree with it. 我被迫答应，但内心并不完全同意。
(2) 后接动词原形(此时to是不定式符号)或动名词(一般有逻辑主语，此时 to 是介词)。如：
We agreed to leave early. 我们同意早点出发。
She agreed to my going home. 她同意我回去。
注：英语不说 agree sb to do sth。如不说：
* She agreed me to go home.
3. agree on [upon]
(1) 主要指双方通过协商而取得一致意见或达成协议。如：
Can we agree on a price (a date)? 我们能不能商定一个价格(日期)?
Both sides agreed on these terms. 双方都同意这些条件。
注：在正式文体中，有时可省略介词 on。如：
Can we agree a price (date)?
(2) 后接动名词，表示同意做某事。如：
He agreed on helping us. 他同意帮助我们。
注：与 agree to do sth 大致同义。所以上句也可说成：
He agreed to help us.
