Economics
Elements Establishing a Valid Contract: Offer and Acceptance
Quick fact
A valid contract does not need to be in writing; a simple verbal exchange of offer and acceptance can create a binding agreement for many types of transactions, as long as there is an intention to be legally bound.
Why this is interesting
You've agreed to buy a friend's bike for $100, but when you show up with the cash, they say 'I changed my mind.' Can you force them to sell? The answer depends on a deceptively simple dance called offer and acceptance.