'to reach AN agreement with someone' It is an idiom. It means to come to an agreement with someone about something. It is also called: 'to reach an accord'

Dear Mugi, It would be helpful to know what you would like to say or in what context you saw if at all the the phrases mentioned above. Thanks Abbas

Both variants are possible.When we use "to reach agreement", the noun "agreement" is uncountable in this case meaning the state of sharing the same opinion or feeling. We use " to reach an agreement" when we mean "to achieve a particular aim".

"Reach an agreement" is the one you should use, both are right but "reach agreement" just sounds plain weird, and I doubt many people use it. You can say: "I reached an agreement with my husband" or "My husband and I reached an agreement" but "I reached agreement with my husband" sounds awkward although it's correct. Oh, the difference is: none, just that one is more used than the other, don't get confused by this and just use "Reach an agreement", there's no difference between them both. PD: Love your hair :D

There's no difference. I've never heard anyone say "reach agreement" though. Hope that helps!