This is the 698th most frequent Persian word.
نفتی
"Nefti" (نفتی) in Persian means "petroleum-related" or "oil-colored (dark greenish-brown)."
Here, 'نفتی' describes a country associated with oil resources.
ایران یک کشور نفتی است.
Iran is an oil-rich country.
In this sentence, 'نفتی' describes the company related to oil industry.
من به شرکت نفتی یک نامه فرستادم.
I sent a letter to the oil company.
The word 'نفتی' here is used to specify that the refinery deals with oil.