For the sense of smell:
* Amoy (formal)
* Baho (informal, usually used for bad smells)
For the act of smelling:
* Amuyin (formal, verb)
* Singhotin (informal, verb, can be used for sniffing)
Examples:
* Ang amoy ng kape ay napakasarap. (The smell of coffee is delicious.)
* Amoyin mo ang bulaklak. (Smell the flower.)
* Ang baho ng basura. (The garbage smells bad.)
* Singhotin mo ang hangin. (Sniff the air.)