"Who" and "whom", "he" and "him", "she" and "her", etc. are a conflation of the old accusative and dative cases, as well as of the genitive case after prepositions. This conflated form is called the oblique case, or the object (objective) case because it is used for objects of verbs (direct, indirect, or oblique) as well as for objects of prepositions. The information formerly conveyed by having distinct case forms is now mostly provided by prepositions and word order. In Old English as well as modern German and Icelandic as further examples, these cases had distinct forms.
Although the traditional terms accusative and dative continue to be used by some grammarians, these are roles rather than actual cases in Modern English. That is, the form whom may play accusative or dative roles (or instrumental or prepositional roles), but it is a single morphological form and therefore a single case, contrasting with nominative who and genitive whose. Many grammarians use the more intuitive labels 'subjective', 'objective', and 'possessive' for nominative, oblique, and genitive pronouns.
Modern English nouns distinguish only one case from the nominative, the possessive case, which some linguists argue is not a case at all, but a clitic.
Interrogative pronouns | Case | Old English | Middle English | Modern English | Masculine/Feminine (Person) | Nominative | hwā | who | who | | Accusative | hwone / hwæne | whom | who / whom1 | | Dative | hwām / hwǣm | | | | Instrumental | | | | | Genitive | hwæs | whos | whose | Neuter (Thing) | Nominative | hwæt | what | what | | Accusative | hwæt | what / whom | | | Dative | hwām / hwǣm | | | | Instrumental | hwȳ / hwon | why | why | | Genitive | hwæs | whos | whose2 |
First person personal pronouns
| Case | Old English | Middle English | Modern English | Singular | Nominative | iċ | I / ich / ik | I | | Accusative | mē / meċ | me | me | | Dative |