Found:

Strong verb

MORPHOLOGY: a term which is used for the class of verbs where inflection is expressed by stem allomorphy or ablaut, that is, by a change of the stem vowel, a change of the stem consonants, or both. EXAMPLE: English: sing:sang:sung, dwell:dwelt:dwelt, and bring:brought:brought, Dutch: loop:liep:gelopen, zit:zat:gezeten.