-iken or -(y)ken
Why the "while" suffix is introduced as -iken in the TipsAndNotes, when it is actually -(y)ken?
Because "iken" can be written separately or be suffixed as -ken when added to consonants or -yken when added to vowels. So, it is originally "iken", which may be the reason it is written like that in the Tips and Notes. I should note that this is just a grammar rule and we almost always prefer to use it as a suffix.
Thanks for the clear explanation! It would be nice to have it in the TipsAndNotes.
-iken can stand alone or be suffixed as -ken when added to consonants or -yken when added to vowels. It is invariable and does not follow the rules of vowel harmony. It does not take further suffixes. iken is used when the verb action is continuous at a point in time. It may also follow an adjective.
Examples; Ben, hasta iken (hastayken), uyurum. I sleep while (when) I am ill. Biz, o hastayken, merak ettik. While he was ill, we worried. Onlar, siz uykuda iken, meşgul olacaklar. They will be busy while you are asleep. Uykudayken, soyuldular. They were robbed while they were asleep.
*Note: The 3rd Person Plural comes from the last verb it is in in the Passive Mood thus states the subject. Subject pronouns are used to make the meaning clear