noun, noun or participle which takes 'suru', intransitive verb
smoking; tobacco use
Refers specifically to smoking tobacco. As 喫煙する it is an intransitive suru-verb meaning to smoke; common in public-health, rules, and facility-related wording such as 喫煙所 and 喫煙禁止.
この建物内での喫煙は禁止されています。
Smoking is prohibited inside this building.
彼は二十歳
He has been smoking since he was around twenty.