filament
noun [ C ] uk/ˈfɪl.ə.mənt/ us/ˈfɪl.ə.mənt/
细丝，细线；长丝
a thin thread or fibre of natural or artificial material
Toothbrushes should be replaced when the filaments become worn. 牙刷毛磨损后就应该更换了。
glass/silk filaments 玻璃／蚕丝
（尤指电灯泡的）灯丝
a thin wire, especially one that lights up inside an electric light bulb
a tungsten filament 钨丝