These words refer to a promise that is backed up in some way and reinforced by the commitment of one’s honour or material possessions. Pledge is the most general of these, applying in any case where someone solemnly promises to remain loyal to a principle or to undertake a given task: a pledge of allegiance to the Crown; a pledge of $1,000 to the flood-relief fund; a pledge to have the alterations completed by Friday. Only the person’s honour backs up his promise in this case. Guarantee is like pledge in that it is a verbal offer, but it is often backed up by an agreement, legal or otherwise, to make good any loss from failure to perform as promised: a money-back guarantee to those dissatisfied with the company’s product; a six-month guarantee on the television set for all repairs that might be necessary during that time.

Bail is a sum of money offered as a pledge by someone charged with a crime, assuring the court that he will appear for trial at a specified time. The alternative to being granted bail is to remain in prison until trial; if the accused fails to appear, his guarantor forfeits the amount pledged as bail . Bond is comparable to bail in that a sum of money is posted, but differs in that the sum is set aside on behalf of someone who is accused of no crime but who might, despite evidence to the contrary, conceivably make off with money or valuables he must deal with directly in his work, or who might fail to fulfil some obligation: firms that place their cashiers under bond ; Trainee teachers are often under a substantial bond to serve for a minimum period after completion of their course. Similar to bond is a recognizance or s surety , either in cash or one’s word, which is entered into as a promise that one will pay a debt, obey certain rules or appear when required: He was released on his own recognizance , pending trial; to enter into one’s own surety .

Collateral indicates the private possessions of value that one puts up when taking out a loan and which one forfeits if the loan is not repaid: She used some shares and some jewellery as collateral for the loan she was taking out. Pledge is sometimes euphemistically substituted for collateral : a loan that stipulated the pledge of her fur coat. Security can also be substituted for collateral , in which case it stresses the retaining of the valuables by the person making the loan. More often, the word refers to a sum of money put up upon signing certain kinds of contracts, as when one leases a house or flat; if the conditions of the contract are not met, the sum may be forfeited: one month’s rent as security , in addition to the first month in advance.