ASSUMPSIT, the Latin word meaning "he has undertaken." It is applied in English law to an obsolete form of action for the recovery of damages by reason of the breach or non-performance of a simple contract, either express or implied, and whether made orally or in writing. Assumpsit was the word always used in pleadings by the plaintiff to set forth the defendant's undertaking or promise, hence the name of the action. See PRACTICE AND PROCEDURE.