The term saya (kanji: 鞘) means "scabbard/sheath" in English. It is written さや in hiragana. It's pronounced roughly like "sah yah".
Refers to different types of sheaths or scabbards, especially among sword collectors. It also refers to the cap for a pen or writing brush. The economic practice of arbitrage is called sayatori, 鞘取り, さやとり (in this case “saya” is written in katakana: サヤ取り), which literally means “taking the sheath”.