a substance, environment, etc within which something else originates or develops

a mould in which something is cast or from which a surface in relief, e.g. a piece of type, is made by pouring or pressing

the natural material in which something, e.g. a fossil, gem, or specimen for study, is embedded

the substance between the cells of a tissue that holds them together

a rectangular array of mathematical elements treated as a unit and subject to special algebraic laws

something resembling a mathematical matrix, esp in rectangular arrangement of elements into rows and columns