This refers to the creation of new words by changing a vowel in an existing word. The past tense of sit is sat and when we sit we often sit on a seat . The past tense of drive is drove and, in the U.S., the past tense of dive is dove . This latter word is interesting as it has never existed in British English. The habit of forming ablaut inflections was obviously so ingrained that we keep inventing them.
Many ablaut forms are no longer as obvious as sit and sat .
Hood and hat , for instance, are ablaut forms. Mike's crutches enter this picture once again as crutch is an ablaut form of crotch which was originally a form of crook . For instance, a dribble is a continuous drip . Jiggle and joggle are repetitive jigs and jogs . Chatter is continual chat .