noun
soft soap; potash soap
A type of soap made with potassium hydroxide, often liquid or semi-solid. Contrasts with カリ石鹸 (potash soap) in some contexts, but here specifically refers to soft soap, especially potash-based.
See also: カリ石鹸
軟石けんはカリウム塩を含むため、固形石けんより柔らかい。
Soft soap contains potassium salts, so it is softer than bar soap.
Compound of 軟 (nan, 'soft') and 石けん (sekken, 'soap'). The term directly describes the physical property of the soap.