The easiest way to remember it is this….you agree to an action, so we use a verb here. You agree on something, so we use a noun.. I agreed to teach my student this evening….we agreed on a price for a lesson at this My girlfriend and I agreed to visit a cafe for lunch. Once there, we couldn’t agree on which pizza to order and share. There are a few exceptions, but this is a good general rule.

But "He agreed to the terms"

"Agree" is a verb that is often followed by a to-infinitive. Here are some examples of other such verbs: "He AGREED to be the leader." "They HOPE to sing." "We can AFFORD to eat chocolate cake." "Please PROMISE to do your homework." But none of these verbs needs to be used in this way: "He AGREED with me." "He AGREED on chocolate cake." "He AGREED for the sake of our relationship." "He AGREED to my presence in the room." "They HOPE for the best." "We can AFFORD chocolate cake." "Please PROMISE me the money" In sentences like "He agreed to the terms of the contract" or "He agreed to my presence in the room", "agreed to" has the same meaning as "accepted".

The phrases "agree to" and "agree on" are close in meaning, but they’re used in slightly different contexts: Agree to – This phrase is typically used when someone consents to a proposal, request, or arrangement. It often implies giving permission or approval to something. Example: "She agreed to the terms of the contract." Here, "agree to" means accepting or consenting to the contract's terms. Agree on – This is used when two or more people reach a mutual decision or share the same opinion about something specific. Example: "We all agreed on the best approach to the project." In this case, "agree on" shows that everyone has come to the same conclusion about the project approach. So, use "agree to" for accepting something that’s been proposed, and "agree on" when people come to a shared decision.

Simon gave you the right answer. In "agree to", "to" is the particle of an infinitive verb and it needs to be followed by the base verb to complete the infinitive. In "agree on", "on" is preposition that needs to be followed by a noun or pronoun that serves as the object of the preposition.