In Germanic languages, weak verbs form their preterites and past participles by means of a dental suffix, an inflection that contains a /t/ or /d/ sound or similar.
Historically, the pronunciation of the suffix in the vast majority of weak verbs (all four classes) was [ð] but, in most sources discussing Proto-Germanic, it is spelled ⟨d⟩ by convention.
It and has been devoiced to /t/ after voiceless consonants and in some other cases (in most Old Norse texts, the alternation is already found in heavy roots, but the light ones preserve /ð/).
Specifically: The class remained small in Gothic, but expanded significantly in the other languages: In Late Old English, further verbs in -can were drawn into this class by analogy, but with umlaut maintained, e.g., bepǣcan "to deceive", past tense bepǣhte, earlier bepǣcte, or wleccan "to warm," past tense wlehte, earlier wlecede.
At the same time, verbs in -ccan were modified to follow the same pattern, as in the new past tense form cwehte alongside earlier cweahte.
The West Germanic languages had a third subclass consisting of short-stem verbs ending in -r (e.g., Old English erian "to plow," nerian "to save," styrian "to stir"), due to West Germanic gemination and subsequent loss of -j- not taking place.
The following is a cross-language paradigm of a short-stem Class I verb **gramjaną "to anger" (Gothic gramjan, Old Norse gremja, Old High German gremmen, Old Saxon *gremmian, Old English gremman, Old Frisian *gremma).
Note that the Old Saxon and Old Frisian verbs given here are unattested, almost certainly due to the small nature of the respective corpora.
The following is a cross-language paradigm of a long-stem Class I verb **hauzijaną "to hear" (Gothic hausjan, Old Norse heyra, Old High German hōren, Old Saxon hōrian, Old English hīeran, Old Frisian hēra) Class II verbs were formed with a suffix -ō-.
In the northern West Germanic languages, an alternative extended suffix -ōja- sometimes appears in the non-past forms, e.g., the Old English infinitive -ian < *-ōjan.
The following is a cross-language paradigm of **laþōną "to invite" (Gothic laþōn, Old Norse laða, Old High German ladōn, lathōn, Old Saxon lathian [-ōjan], ladian [-ōjan], Old English laþian, Old Frisian lathia).
The present tense was conjugated as a strong verb, for example, Gothic fullna, fullnis, fullniþ, etc.
However, for a time in the 18th century, the forms fragen, frug, gefragen by analogy with, for example, tragen (to carry) were also considered acceptable in the standard.
While primary verbs (those inherited from PIE) already had an ablaut-based perfect form that was the basis of the Germanic strong preterite.
The denominative in Indo-European and early Germanic was formed by adding an ablauting thematic *-yé⁄ó- suffix to a noun or adjective.
They are formed in a way that reflects a direct inheritance from the PIE causative class of verbs.
That method of forming causative verbs is no longer productive in the modern Germanic languages, but many relics remain.
That was the case with the Gothic verbs waurkjan "to work, create," bugjan "to buy," and sokjan "to seek."
Perhaps the most commonly held theory is that it evolved out of a periphrastic construction with the verb *dōną to do: Germanic **lubō-dē- ("love-did") > *lubōdē- > Old English lufode > loved or **salbō-dē- ("salve-did", i.e., "put salve") > **salbōdē- > Old English sealfode > salved.
That view is not without objections:[citation needed] The objections are sometimes answered as follows:[citation needed] Another theory is that it came from a past participle ending, a final *-daz from PIE *-tos (compare Latin amatus), with personal endings added to it at a later stage.
According to Hill (2010), the endings, which in the singular do not show reduplication in any Germanic language, continue the PIE subjunctive of the root aorist.
[citation needed] The term "weak verb" was originally coined by Jacob Grimm, who only applied it to Germanic philology.