wǣron ("to be") Modern English: was – were Old English: cēosan, cēas – curon coren ("to choose") Old English: frēosan, frēas – fruron froren ("to freeze") Old Norse (early): vesa, vas – váru ("to be", the -s- was soon replaced by -r- analogically) Old Norse: frjósa, frýss – fruru, frorinn ("to freeze") Modern Dutch: wezen, wees, was – waren ("to be") Modern Dutch: verliezen, verlies – verloor, verloren ("to lose") Modern Dutch: vriezen, vries – vroor, gevroren ("to freeze") NB. Not all consonant apophony in Germanic verbs is caused by . The consonant alternation in certain weak verbs which typically goes along with the phenomenon (think:thought, German denken:dachte) is a result of a later development in Germanic known as the Germanic spirant law. Likewise, the terminal devoicing which produces a fortis-lenis alternation in Dutch (wrijven:wreef) is an unrelated historical phenomenon. Between strong verbs and derived causatives In PIE, causative verbs (meaning "to cause to") were derived from verb roots with a suffix *-éye-, and the root vowel was changed to the o-grade. Verbs with this suffix eventually became part of the first weak class (*-jan verbs). This suffix always bore the accent, and the verb root never did, while in regular strong verbs the verb root was accented in the present tense. This caused Verner alternation between the original verbs and the causative verbs derived from them. Examples are numerous in the older languages but are less frequent today, because some levelling has occurred, and in some cases, one verb or the other was lost. *f ~ *b Although technically not a strong verb - causative pair, modern Dutch shows the alternation in a verb with the same underlying Proto-Germanic shape. heffen ("to lift/raise", from the strong verb *habjaną) - hebben ("to have", from the weak verb *habjaną) *þ ~ *d Modern German: leiden ("to suffer, to undergo", originally "to go", from *līþaną) – leiten ("to lead", from *laidijaną) *h ~ *g Modern Icelandic: hlæja ("to laugh", from *hlahjaną) – hlægja ("to make laugh", from *hlōgijaną) *hw ~ *gw/w/g (No attested examples within a single language) Gothic þreihan ("to press", from *þrinhwaną) – German drängen ("to push", from *þrangwijaną) *s ~ *z Modern English: rise (from *rīsaną) – rear (from *raizijaną) Modern Dutch: genezen ("to heal", from *ganesaną) – generen ("to take care of oneself", from *nazjaną) Modern German: genesen ("to heal", from *ganesaną) – nähren ("to feed", from *nazjaną)