An agreement of any kind is a [?]. When you reach an agreement, you can talk about [?] or [?].
A [?] is also an agreement reached through negotiation. People who get what they want in a negotiation are said to [?].
An agreement may be in the form of a [?]. "Contract" is used in these combinations:

An [?]/ a labour contract (BrE)/ labor contract (AmE) is about what someone has to do in their job, or about what a particular group of employees have to do.
An [?] is not written down.
A [?]/[?] forces both sides to carry out the actions that they had promised to carry out, by law.
A [?] is about buying or selling a product.