1) Isarithm 2) Isogram 3) Isopleth 
line connecting points of equal time difference or simultaneous occurrence
A set of points with the property that a given process or trajectory will take the same length of time to complete starting from any point in the isochrone. The curve formed by such a set of points is called an isochronous curve. Related entry • tautochrone problem
A line on a map or chart that connects points at which an event occurs simultaneously or which represents the same time or direction.
[n] - an isogram connecting points at which something occurs or arrives at the same time
isochrone A line on a chart connecting all points having the same time of occurrence of particular phenomena or of a particular value of a quantity. Related-word units meaning same: auto-; equ-; homeo-; homo-; pari-; peer-; syn-; tauto-.
noun an isogram connecting points at which something occurs or arrives at the same time
a line, as on a map, connecting all points having some property simultaneously, as in having the same delay in receiving a radio signal from a given source or requiring the same time to be reached by available transportation from a given center.