Is there any real difference between "two-sided contracts" and "bilateral contracts"? (And also between "one-sided contracts" and "unilateral contracts"?)

After scouring the web, it seems that in both pairs the terms are often used as synonyms. But could there still be difference in meaning? Even a very small one?

2 Answers 2


I agree with @ohwilleke's answer for the most part, but see below for corrections:

What he described as a unilateral contract is instead more likely a contract of adhesion. An adhesion contract is a standard form contract, written by one party (usually the one with more bargaining power), and presented to the (usually) the weaker party and the weaker party does not typically have the power to negotiate or change the terms before signing. These are carefully scrutinized by courts and are often found to be unenforceable due to the problems that arise with them, mostly that the terms would require the weaker party to perform something beyond what his reasonable expectations would have been when signing the contract.

What a unilateral contract actually is: a contract between parties to do or not do some act or acts and where one party pays the other party to perform the duty/duties included in the contract. Here, one party is legally obligated to uphold the contract's terms (the person making the payment). A simple example is if you have a missing pet and you place an ad in the paper offering a reward for its return. Nobody is legally obligated to bring you your pet back; however, if somebody does bring it back, you would likely be legally obligated to pay out the reward.


A bilateral agreement or bilateral contract is an agreement with two parties as opposed to one with more than two parties. It has no real connotations and is strictly a descriptive term

A unilateral contract is a contract proposed by one party on a take it or leave it basis to one or more other parties to accept. Once accepted, it is often simultaneously a unilateral contract and a bilateral contract.

A one-sided contract is a contract whose terms favor one side in an extreme manner to the detriment of another. A unilateral contract could be one-sided, but could also be balanced and fair.

A two-sided contract is a contract whose terms balance the interests of the parties to a bilateral contract significantly rather than only favoring one side of the agreement to the detriment of the other, generally due to negotiations over the terms of the contract when it was originally drafted (even if it is reused by people who don't themselves negotiate its terms).

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    I would upvote this answer if it had any references to another source or other sources. I mean, it makes very good sense, but it gives me no confidence that these terms are generally understood to have these meanings. I'd also add that a bilateral contract could be one-sided under these definitions, especially if the contracting parties do not have a relatively even balance of power.
    – phoog
    Dec 3, 2017 at 20:43

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