Bu kaçıncı ders?

Which lesson number is this?

Breakdown of Bu kaçıncı ders?

• bu: this
• ders: the lesson
• kaçıncı: which one (in a sequence)?

Questions & Answers about Bu kaçıncı ders?

What does each word in Bu kaçıncı ders? mean?

• Bu = this
• kaçıncı = which one in order / what number
• ders = lesson, class

So the sentence literally means something like This, which-number lesson? In natural English, that becomes Which lesson is this? or What number lesson is this?

What does kaçıncı mean, and how is it formed?

Kaçıncı asks about position in a sequence: first, second, third, and so on.

It comes from:

• kaç = how many
• the ordinal suffix -(I)ncI = a suffix that makes ordinal forms

So:

• kaç = how many
• kaçıncı = which number in order / the how-many-th one

The suffix changes form because of vowel harmony, so here it appears as -ıncı.

Why is there no word for is in the sentence?