"I have his number."
Translation:Ich habe seine Nummer.
Nummern designate ranks and orders, and represent other things, like the numbers in addresses, phone numbers, page numbers, etc. Zahlen are quantities and can be added, subtracted, etc, like the numbers in math problems, amounts of money, etc.
I have seen both "seine Nummer" and "seiner Nummer" shown as correct in this one. Are they both correct?
seiner is wrong. You'd only use seiner Nummer for dative or genitive cases. "Nummer" is in the accusative case in this example; and since it's a die-word, there's no change.
Would this phrase ever be used in an idiomatic sense like it exists in English? "I have his number" could in English mean that "I know how to deal with him" or something similarly sinister.
Well, it means "his". But the ending depends on the gender of whatever noun belongs to him:
der Hut - sein Hut
die Uhr - seine Uhr
das Haus - sein Haus
Da ist mein Hut. Wo ist seiner? -- (T)here's my hat. Where is his?
Da ist meine Uhr, wo ist seine?
Da ist mein Haus, wo is seines?
While both sentences would have the same geberal meaning, alteration of word order is not without some consequence. German allows several parts of the sentence to be rearranged, but doing so will change the emphasis. So, I guess that putting "seine Nummer" in the front has a slightly different feel and meaning.
On another exercise, someone commented the exact opposite, so now I'm confused.
ihme is not a word.
"I have his number. - Ich habe seine Nummer."
"I have her number. - Ich habe ihre Nummer."
Sein means his, and you add endings to it depending on the gender and case of the noun being described. Ihme is not a word, but if you are thinking of ihm, that is the dative form of him, and if you are thinking of ihre, ihr means her (as in the possesive form, like her car).
der Hut: Ich habe seinen Hut.
die Uhr: Ich habe seine Uhr.
das Glas: Ich habe sein Glas.
Also, see the other comments in this thread.
I thought the possesive pron. was determined by the grammatical gender of the possesor. Or is it based on the object being possesed like in french?
Is it "Das Mächen hat ihre Hund"
"Das Mädchen hat sein Hund"?
The girl has her dog -- Das Mädchen hat seinen Hund. Since Hund is masculine, haben puts it in the accusative case. It's seinen, because Das Mädchen is neuter.
The woman has her dog -- Die Frau hat ihren Hund. Hund and haben determine the case-ending, Frau being feminine determines the possessive ihr-.
The boy has his dog. -- Der Junge hat seinen Hund.
Das Mädchen hat seine Katze / Die Frau hat ihre Katze / Der Junge hat seine Katze
Das Mädchen hat sein Lamm / Die Frau hat ihr Lamm / Der Junge hat sein Lamm
Slight correction: "The girl has her dog" is "Das Mädchen hat ihren Hund", and same with the other sentences with "Mädchen" in them. Sein and it's variations mean his, and ihr and it's variations mean her, regardless of the grammatical gender of the noun. Since the girl is female, even though the word "Mädchen" is neuter, we would use ihr in this case.
What I wrote is correct. "ihr" means "her" or "its" and depends on the grammatical gender of the noun. No one will look at you like you're a terrible german speaker if you say "Das Mädchen hat ihren Hund", and you might even hear Germans saying it this way, because yeah, the girl's female. But, if you want to have a grammatical discussion with someone, then "Das Mädchen hat seinen Hund" will win. "Sein" is used for both Masculine and Neuter singular nouns, and "ihr" is used for feminine singular nouns.
This has probably been brought up elsewhere, but is "Ich hab seine Nummer" actually wrong. I know that "hab" is considered more casual, but I thought it was accepted German at this point.
That's how I say it and how I type it in text messages. But, in a book or in the news, you'll read "habe".