This is the 496th most frequent Romanian word.
pur
Pure.
Here, 'pur' is an adjective describing the quality of air, meaning clean and uncontaminated.
Aerul din munți este pur.
The air in the mountains is pure.
In this context, 'pur' is used as an adverb to emphasize the personal nature of the decision.
Decizia lui a fost una pur personală.
His decision was purely personal.
Here, 'pur' is part of the phrase 'pur și simplu,' which translates to 'simply' and is used to indicate straightforwardness.