in general, denotes any act by which a person becomes bound to another to do something, as to pay a sum of money, be surety, or the like. Obligations are of three kinds; natural, civil, and mixed. Natural obligations are entirely founded on natural equity; civil obligations rest on civil authority alone, without any necessary foundation in natural equity; and mixed obligations are those which, being founded on natural equity, are besides enforced by civil authority.

In a legal sense, obligation signifies a bond, in which is contained a penalty, with a condition annexed, for the payment of money, or the performance of some act. The difference between it and a bill is, that the latter is generally without a penalty or condition, though it may be made obligatory; and obligations are sometimes incurred by matter of record, as statutes and recognizances.