West Germanic
- At some point between the late Proto-Germanic and Proto-Northwest Germanic, the Instrumental and dative plural endings had begun syncretizing.
- The second-person plural *jūz and dual *jut pronouns were adjusted to *jiz (compare Old Norse èr, Old english ġē, Old saxon gē~gī) and *jit (compare Old Norse it, Old English ġit, Old Saxon git) under the influence of the first-person *wiz and *wit.
- In Proto-Germanic, present participles were consonant stems which ended in -nd-, with feminines ending in -ndī~-ndijō. In Proto-West-Germanic, masculine and neuter present participles regardless of gender ended in -ndija-, which was probably backformed from the feminines.
- A small number of inherited neuter collectives like *sēmô "seed" (cognate with Latin sēmen), *namô "name" (cognate with Latin nōmen, Ancient Greek ὄνομα) were transferred to masculine singulars in the n-stem class.
- The third-person pronoun *i-~*e- was replaced with *hi-~*he- in the southern West Germanic dialects. Additionally, the feminine nominative singular *sī acquired the usual feminine ending *-u, becoming *siju (however, *sī is attested in Old High German).
- The demonstratives *sa (masculine nominative singular) and *sū (feminine nominative singular) were replaced with *siz and *siju under the influence of the third-person pronoun.
Old English
- Strong verbs whose roots ended in *f had their Verner alternations destroyed when *[β] and *f merged into v word-internally, and into f word-finally (both [f] and [v] were written f).
- The instrumental case merged into the dative case.
- Nominative and accusative plurals merged in nouns.