§ 150. In Old English, as in all Germanic languages, verbs fall into two large classes, the Strong and the Weak. Strong verbs comprise: (a) Non-Reduplicating or Graded Verbs, i.e. those which form their preterites and past participles by a change of the root vowel (see Vowel Gradation, Chap. V, § 53), as rīdan, to ride, pret. rād, ridon, past part, riden; (b) Reduplicating Verbs (§ 170), i.e. those which at an earlier period, as seen in Gothic, formed their preterites by a reduplicating prefix which consisted of the initial consonant of the stem and the vowel e (Gothic aí). These verbs occurred with and without gradation. In O.E., however, very few cases of reduplication remain, and these verbs also apparently form their preterites by change of vowel only, as for example hātan, to command, to which the usual preterite is hēt, hēton, and the past participle hāten, but to which a reduplicating preterite heht, corresponding to the Gothic haíháit, is sometimes found.