A bond is an obligation or contract made binding by a forfeit of money. Bonds are either single (simple) or double (conditional). A single bond is one in which the obligor binds themselves, their heirs, etc. to pay a certain sum of money to another person on a specified day. A double bond is one to which a condition is added that if the obligor does or forbears from doing some act the obligation shall be void. Sometimes such a condition was contained in a separate instrument, and was then called a “defeasance.”