This is the 448th most frequent Romanian word.
ultimii
"Ultimii" means "the last ones" in English.
In this sentence, 'ultimii' is used as a masculine plural form referring to the 'three chapters' that are at the end.
Am citit ultimii trei capitole ale cărții.
I read the last three chapters of the book.
Here, 'ultimii' refers to people (students) in the masculine plural form who were the last ones to leave.
Ultimii elevi au plecat după ora șase.
The last students left after six o'clock.
In this case, 'ultimii' qualifies 'ani' (years), which is a masculine plural noun, indicating the most recent years.