WEAK VERB ..
Those weak verbs which add -d or -ed to form past tense and past participle and no change of vowel, are so easilly recognizedas to need no special treatment.
In Germanic languages, weak verb are by far the largest group of verbs, which are therefore often regarded as the norm, though historically, they are not the oldest or most original group.
In Germanic Languages, strong verb is one which marks its past tense by means of ablaut.
In English, these are verbs like sing, sang, sung. The term ' strong verb ' is a translation of German 'starkes verb', which was coined by a linguist Jacob Grimm