knife： A cutting instrument, consisting of a blade with a sharpened longitudinal edge fixed in a handle, either rigidly as in a carving knife (carving-knife at carving n. 4a), sheath-knife, or table-knife (table knife n. at table n. Compounds 3), or with a joint as in a clasp-knife (clasp-knife n.) or pocket-knife (pocket knife n.). The blade is generally of steel, but sometimes of other material, as in the silver fish- and fruit-knives, the (blunt-edged) paper knife (paper knife n.) of ivory, wood, etc., and the flint knives of early man. ——Oxford English Dictionary  @zh

锋利长刃固定在刀柄上所组成的切割用具，可分成固定式的，例如餐刀、凋刻刀，或是附有刀鞘的刀；以及带有接合点的，例如口袋刀或折叠刀等。刀可用于切割食物，特别是用于供应和食用饭菜，也可用作武器以及其他用途。刀刃可以用钢、其他金属或石头制作，例如早期人类所使用的燧石刀，或是以象牙、木头（如裁纸刀）等其他材质制作而成。该词语亦指形状或用途类似刀的工具，即便边缘并没有特别锐利，或实际上未作为切割之用。——AAT-台湾  @zh

刀  @zh