What type of contract is characterized as unilateral?

A unilateral contract is defined by the fact that it includes a promise made by only one party, creating an obligation that is contingent upon the actions or performance of the other party. Option contracts are a prime example of unilateral contracts because in this scenario, one party grants another the right to buy or sell an asset at a predetermined price within a specific timeframe. The promise made by the option buyer to purchase is contingent upon the seller's performance of keeping the offer open, but the seller is not required to act unless the buyer decides to exercise the option.

In contrast, lease contracts typically involve reciprocal obligations where both the lessor and lessee have duties to fulfill, such as paying rent and providing a habitable space. Joint venture and partnership contracts also both engage multiple parties in mutual agreements and responsibilities, thereby not fitting the definition of unilateral contracts since they involve promises from all parties involved.