This is the 797th most frequent Greek word.
κτίριο
Building.
In this sentence, 'κτίριο' is used as a standalone noun to refer to a specific building whose age is described.
Το κτίριο στην άκρη του δρόμου είναι παλιό.
The building at the end of the street is old.
Here, 'κτίρια' is used in its plural form to refer to multiple structures within a certain area.
Αυτή η περιοχή έχει πολλά μοντέρνα κτίρια.
This area has many modern buildings.
In this example, 'κτίριο' is used as the subject of the sentence to describe the object that underwent construction.