Agreement (linguistics) - Wikipedia
https://en.wikipedia.org/wiki/Agreement_(linguistics)Agreement or concord (abbreviated agr) happens when a word changes form depending on the other words to which it relates. It is an instance of inflection, and usually involves making the value of some grammatical category (such as gender or person) "agree" between varied words or parts of the sentence. For example, in Standard English, one may say I am or he is, but not "I is" or "he am". This is becau…