Instrumental Case in Kazakh (-мен/-бен/-пен)

The *Instrumental Case (Көмектес септік) is a defining feature of the Kazakh nominal declension system. Unlike Modern Turkish—which dropped the historical Turkic instrumental case and replaced it with the cliticized postposition ile—Kazakh retains the instrumental as a full 7th grammatical case with three harmonious variants (-мен / -бен / -пен*):

1. -мен: Attached after vowels (а, е, ы, і), and the sonorants р, л, й, у, м, н, ң: - баламен* (with the child), үймен (with/by house), қаламмен (with a pen), досыммен (with my friend). 2. -бен: Attached after the voiced consonants ж, з: - қызбен (with the girl), қағазбен (with paper), көзбен (with the eye). 3. -пен: Attached after all voiceless consonants (к, қ, п, с, т, ш, ф, х): - кітаппен (with/by a book), пойыз*бен (exception: з takes -бен) / автобуспен* (by bus), пышақпен* (with a knife).

Core Semantic Functions: - Accompaniment / Togetherness ('with'): Асқар досымен келді (Asqar came with his friend). - Instrument / Tool ('by means of'): Қаламмен жаздым (I wrote with a pen). - Mode of Transport: Ұшақпен ұштық (We flew by airplane), Пойызбен бардық (We went by train).

Notice that unlike other Kazakh suffixes, the vowel in -мен/-бен/-пен does not undergo back/front vowel harmony (it is always е).