Agreement

An agreement may be an agreement in beliefs, rules, practices (policies), or conduct.—

an agreement between individuals to follow a specific course of conduct -- whether it be moral, e.g., not to kill or harm each other, or immoral, e.g., to kill or harm an innocent individual.
in law, a legally binding contract enforceable in a court of law.
in linguistics, rules that exist in many languages that force some parts of a sentence to be used or inflected differently depending on certain attributes of other parts. See grammatical gender, grammatical number, and grammatical person.
in economics, the definition of money as an "agreement within a community to use something as a medium of exchange", the agreement may be voluntary or coerced, conscious or unconscious, and may fluctuate with time or remain fixed.

See also