This is the 2002nd most frequent Turkish word.
seviyesi
"Seviyesi" means "level" or "degree" in English.
In this sentence, "seviyen" refers to the individual's proficiency or skill level in the Turkish language course.
Türkçe dersinde seviyen çok yüksek.
Your level in Turkish class is very high.
Here, "seviyesi" is used to denote the height or measurement level of the sea.
Deniz seviyesi her yıl birkaç milimetre yükseliyor.
The sea level rises by a few millimeters every year.
In this context, "dil seviyesi" describes the complexity or difficulty level of the language in the book.