This is the 5447th most frequent Turkish word.
kısmını
The Turkish word "kısmını" means "its part" or "the part of it."
Here, 'kısmını' denotes a possessive relationship to 'kitabın', indicating 'part of the book' as the object of the sentence.
Kitabın önemli bir kısmını okudum.
I read an important part of the book.
In this usage, 'kısmını' is used to specify a particular section of 'bu pastanın', describing 'the tastiest part' as the object receiving the action.
Bu pastanın en lezzetli kısmını yedi.
They ate the tastiest part of this cake.
'kısmını' here specifies 'the last part' of 'toplantının', indicating it as the object impacted by the action of missing in the sentence.