The term katana (kanji: 刀) means "sword" in English. It is written かたな in hiragana. It's pronounced roughly like "kah-tah-nah".
Katana can be used to refer to a particular type of sword in the family of nihontoNIHONTO 日本刀 "Japanese sword" learn more... (“Japanese swords”), but it is more widely used as a catch-all term. So, the average Japanese would say that a samuraiSAMURAI 侍 "warrior serving a lord" learn more... carries a katana and a tantoTANTO 短刀 "short sword" learn more..., but they would leave it to the experts to get more specific than that.
On the other hand, you would not say that a samurai carries a nihonto, as that would be awkward and redundant. (The word nihonto is usually employed for scholarly purposes.)