A yan is a type of ceremonial bladed sword used by some Klingon warriors. Kurn had a pair of yans hanging in his office aboard the IKS Hegh'ta, as did Lursa and B'Etor aboard their ship. (TNG: "Redemption")
Like his brother, Worf also kept two crossed yans in his quarters aboard the USS Enterprise-D. (TNG: "Reunion", "Night Terrors")
During his exercise program on the holodeck, Worf and K'Ehleyr used a pair of yans to defeat computer-generated opponents. (TNG: "The Emissary")
Duras utilized a yan in his duel with Worf in 2367. He was killed by Worf and his bat'leth. (TNG: "Reunion")
Governor Vagh of Krios also had two crossed yans on display in his office. (TNG: "The Mind's Eye")
These weapons were never named on-screen. (citation needed • edit)