The phrase "by agreement" refers to a situation where two or more parties have come to a mutual understanding about a particular matter. It is often used in legal and business contexts to describe contracts, settlements, or partnerships that have been agreed upon by all parties involved. Some synonyms for "by agreement" include "mutually agreed," "by mutual consent," "by common understanding," "by arrangement," "by understanding," and "by concurrence." These phrases all suggest a sense of cooperation and collaboration, and they can be used interchangeably to describe situations where parties have come to an agreement through dialogue and negotiation.