The nominative case (abbreviated nom) is one of the grammatical cases of a noun or other part of speech, which generally marks the subject of a verb or the predicate noun or predicate adjective, as opposed to its object or other verb arguments. (Generally, it is a noun that is doing something.)
The reference form (more technically, the least marked) of certain parts of speech is normally in the nominative case, but this is often not a complete specification of the reference form, as it may also be necessary to specify eg the number and gender. Thus the reference or least marked form of an adjective might be the nominative masculine singular. The parts of speech which are often declined and therefore may have a nominative case are nouns, adjectives, pronouns and less frequently numerals and participles. The nominative case often indicates the subject of a verb, but sometimes does not indicate any particular relationship with other parts of a sentence. In some languages the nominative case is unmarked, that is, it takes the form of the word stem, with no inflection; alternatively, it may be said to be marked by a zero morpheme. Moreover, in most languages with a nominative case, the nominative form is the lemma; that is, it is the reference form used to cite a word, to list it as a dictionary entry, etc.
Nominative cases are found in Slovak, Lithuanian, Georgian, German, Latin, Icelandic, Old English, Polish, Czech, Romanian and Russian,Pashto, among other languages. English still retains some nominative pronouns, which are contrasted with the accusative (comparable to the oblique or disjunctive in some other languages): I (accusative, me), we (accusative, us), he (accusative, him), she (accusative, her) and they (accusative, them). A usage that is archaic in most, but not all, current English dialects is the singular second-person pronoun thou (accusative thee). A special case is the word you: Originally ye was its nominative form and you the accusative, but over time you has come to be used for the nominative as well.
In active-stative languages there is a case sometimes called nominative which is the most marked case, and is used for the subject of a transitive verb or a voluntary subject of an intransitive verb, but not for an involuntary subject of an intransitive verb; since such languages are a relatively new field of study, there is no standard name for this case.
Some writers on English grammar employ the term subjective case instead of nominative, in order to draw attention to the differences between the "standard" generic nominative and the way it is used in English.
Generally, when the term subjective case is used, the accusative and dative are collectively labelled as the objective case. This is possible in English because the two have merged; there are no surviving examples where the accusative and the dative are distinct in form, though their functions are still distinct. The genitive case is then usually called the possessive form and often is not considered as a noun case per se; English is then said to have two cases, the subjective and the objective. This view is an oversimplification, but it is didactically useful.