insure

Concise Oxford English Dictionary © 2008 Oxford University Press:
insure /ɪnˈʃʊə/

▶verb

• 1 arrange for compensation in the event of damage to or loss of (property, life, or a person), in exchange for regular payments to a company.

  ■ secure the payment of (a sum) in this way.

• 2 (insure someone against) protect someone against (a possible eventuality).

• 3 another term for ensure.

– derivatives
insurability noun,
insurable adjective,
insurer noun.

– origin ME: alt. of ensure.

usage: There is considerable overlap between the meaning and use of insure and ensure. In both British and US English the primary meaning of insure is ‘arrange for compensation in the event of damage or loss’; ensure is not used at all in this sense. For the general senses, insure and ensure are often interchangeable, but insure tends to be more common in US English.