- In common meteorological usage, a line of equal or constant value of a given quantity, with respect to either space or time;
same as isogram.
- (Also called isarithm.) A line drawn through points on a graph at which a given quantity has the same numerical value (
or occurs with the same frequency) as a function of the two coordinate variables.
Compare isotimic line. - A straight line along which lie corresponding values of a dependent and independent variable.