Beyging mannanafna — declining people's names

Names decline too

Icelandic personal names take case endings like any noun — there is no escaping it, because every sentence about a person puts their name in a case.

Strong masculine names add -i in the dative and -s in the genitive: Jón → Jóni → Jóns, Halldór → Halldóri → Halldórs. Weak feminine names in -a go to -u everywhere outside the nominative: Anna → Önnu (with the u-umlaut you know). Names in -ún like Guðrún take -u / -ar: Guðrúnu, Guðrúnar.

Surnames in -son and -dóttir decline the same way: ég talaði við Jón Jónsson — bókin er eftir Guðrúnu Jónsdóttur.

The pattern to internalise: ég hjálpaði Jóni (dative verb), ég hitti *Önnu* (accusative), *bíllinn hans Jóns* (possession, as you drilled at B1).