This is the 1357th most frequent Turkish word.
projesi
"Projesi" means "project" or "the project" in English.
Here, 'projenin' (of the project) is the possessive form showing ownership by the project, and it modifies 'tamamlanması' (completion).
Bu projenin tamamlanması iki yıl sürdü.
The completion of this project took two years.
In this sentence, 'projesi' (project) is used with the possessive suffix '-si' indicating that the project belongs to 'arkadaşım' (my friend).
Arkadaşımın projesi çok yaratıcı bulunuyor.
My friend's project is found very creative.
Here, 'projesi' (project) has a possessive suffix '-si' attached to the word 'proje', denoting possession.