Learn Turkish: Uykunun bu evresinde deliksiz uyuyabildi. - In this phase of sleep, he was able to sleep soundly.

Deliksiz literally means "without holes" or "seamless." When used to describe sleep (uyku), it is a very common idiom meaning "uninterrupted," "deep," or "sound" sleep.

Since our current lesson is about the o kadar ... ki construction, how could we rewrite this sentence to use it?

You could emphasize the depth of the sleep by placing o kadar before the adverb: Uykunun bu evresinde o kadar deliksiz uyuyabildi ki... (In this phase of sleep, he was able to sleep so soundly that...). You would then follow the ki with a result clause, such as çalar saati bile duymadı (he didn't even hear the alarm clock).

Let's review the suffixes on evresinde. Why is there an -n- before the -de?

This word is part of the possessive compound uykunun evresi (the phase of sleep). The word evre (phase) takes the third-person possessive suffix -si. Whenever you add a spatial case ending like the locative -de (in/at/on) to a third-person possessive suffix, Turkish requires the buffer letter -n-, making it evresinde.

How would we change uyuyabildi (he was able to sleep) into the negative "he couldn't sleep"?