A category covering knives built from multiple layers of different steels forge-welded together. The hard cutting steel is sandwiched between softer outer layers (cladding) that protect the core, add toughness, and often contribute visual contrast.
The most common laminated constructions in the Modern Cooking catalogue are:
SanMai (三枚) — three layers: hard cutting steel in the centre, softer cladding on both sides. The traditional and most common form.
GoMai (五枚) — five layers: a hard core, two intermediate layers, and two outer layers. Adds visual depth and structural complexity.
KuMai (九枚) — nine layers: similar logic, with more cladding layers for additional pattern and structural variation.
GoMai and KuMai are often chosen not only for the additional layers and visual depth, but also because the intermediate layers can act as a nickel diffusion barrier — limiting carbon migration out of the core into the cladding during forge welding, and protecting the core's intended carbon content through the heat of the forging process.
In all cases the cutting performance is determined by the core steel; the outer layers are cosmetic and structural. The lamination contributes corrosion protection (when a stainless jacket clads a carbon core), reduced reactivity, and the visible boundary between core and cladding that gives the knife its character.