Hatch mark

Hatch marks (also called hash marks or tick marks) are a form of mathematical notation. They are used in three ways as:

• Unit and value marks — as on a ruler or number line
• Congruence notation in geometry — as on a geometric figure
• Graphed points — as on a graph

Hatch marks are frequently used as an abbreviation of some common units of measurement. In regard to distance, a single hatch mark indicates feet, and two hatch marks indicate inches. In regard to time, a single hatch mark indicates minutes, and two hatch marks indicate seconds.

In geometry and trigonometry, such marks are used following an elevated circle to indicate degrees, minutes, and seconds — ( ° ) ( ′ ) ( ″ ).

Hatch marks can probably be traced to hatching in art works, where the pattern of the hatch marks represents a unique tone or hue. Different patterns indicate different tones.