A necklace is a piece of jewelry used as a clothing accessory, worn on the neck.
In 2293, Klingon Chancellor Gorkon occasionally wore a silver-colored necklace that his daughter, Azetbur, inherited after Gorkon was assassinated later that year. (Star Trek VI: The Undiscovered Country)
In 2364, Anne Jameson wore a necklace during the time she visited the USS Enterprise-D with her husband, Admiral Mark Jameson. (TNG: "Too Short a Season")
The Kataan native Eline wore a necklace shaped like the Kataan probe. (TNG: "The Inner Light")
In 2369, Vash secured a gold necklace she brought from her trip into the Gamma Quadrant in a storage locker of the assay office aboard Deep Space 9. (DS9: "Q-Less")
Vash herself wore a necklace which was not put around her neck but attached to her earrings. (TNG: "Qpid", DS9: "Q-Less")
The Bajoran Kai Opaka gave Miles O'Brien her necklace, including a pendant, shortly before she left Deep Space 9 in 2369. O'Brien gave it to his daughter. (DS9: "Battle Lines")
Arbazan Ambassador Taxco wore a golden necklace during her visit aboard Deep Space 9. (DS9: "The Forsaken")
A necklace was one of the items stolen by a Dopterian thief in Quark's in 2369. (DS9: "The Forsaken")
The Iyaaran ambassador Voval, disguised as Anna, wore a necklace which allowed him to create this illusion to study the concept of love with Captain Picard. (TNG: "Liaisons")
In 2375, the Starfleet soldier Reese wore a necklace of ketracel-white tubes he took from the Jem'Hadar he killed on AR-558. (DS9: "The Siege of AR-558")