A Maple dimension is a product of rational powers of symbols or functions of symbols whose arguments are symbols, where the symbols are base dimensions in the Units package.

The type(expr, dimension) and type(expr, dimension(base)) calling sequences return true if expr has the form of valid output from the function convert/dimensions with the base=true option, that is, a function of base dimensions.

The type(expr, dimension(derived) calling sequence returns true if expr is a derived dimension with a special name or type(expr, dimension) would return true.

If a second option p is given and type/dimension returns true, the function of base dimensions corresponding to expr is assigned to p.