seinem

Seinem is the dative singular form of the German possessive determiner sein, meaning “his” (or “its” when referring to a neuter neuter noun). It is used to indicate possession and to agree with the gender and case of the noun it modifies. Specifically, sei m is used before masculine or neuter singular nouns in the dative case.

In contrast to sein, the feminine dative form is seiner, and the dative plural form is seinen. For reference, the full declension of sein as a possessive determiner in the singular and plural is:

- Masculine: Nom sein, Gen seines, Dat seinem, Acc seinen

- Feminine: Nom seine, Gen/seiner, Dat/seiner, Acc seine

- Neuter: Nom sein, Gen seines, Dat seinem, Acc sein

- Plural: Nom seine, Gen/seiner, Dat/seinen, Acc seine

In sentences, sein/sein(e)m agrees with the noun it accompanies. Examples:

- Ich helfe seinem Bruder. (I help his brother.)

- Wir vertrauen seinem Rat. (We trust his advice.)

- Er gab seinem Auto neue Felgen. (He gave his car new rims.)

- Ich gratuliere seiner Schwester zum Geburtstag. (I congratulate his sister on her birthday.)

Seinem is not used on its own as a pronoun; it functions as a determiner that accompanies a noun. Its use is common in both written and spoken German and is essential for correctly expressing possession in the dative construction. The form reflects the possessor (third-person masculine/neutral) and the grammatical role of the noun within the sentence. Etymologically, sein derives from the old and middle forms of the Germanic possessive pronoun, with the current inflectional system inherited from historical noun declensions.