This is the 3686th most frequent Russian word.
трети
"Трети" means "thirds" in English.
The word 'трети' is used here in its fractional form to describe a portion of a whole, specifically two-thirds.
Две трети студентов успешно сдали экзамен.
Two thirds of the students passed the exam successfully.
Here, 'трети' is used figuratively to describe a portion or segment belonging to a third of the total.
Я купил несколько трети песчаных дюн в пустыне.
I bought a few third parts of the sand dunes in the desert.
The word 'третий' (related to 'трети') is an ordinal number describing the sequence of floors in a building, though the inflection changes.