How is the size of an outdoor motor propeller typically measured?

The size of an outdoor motor propeller is typically measured using diameter and pitch. The diameter refers to the overall width of the propeller, representing the distance across the circle that the blades create when they spin. This measurement is essential as it affects the amount of air moved by the propeller, which is critical for its performance.

Pitch refers to the theoretical distance a propeller would move forward in one complete rotation, akin to a screw's lead. This measurement indicates how much 'bite' the propeller has in the air and directly influences the speed and efficiency of the motor. Together, these two measurements provide a comprehensive understanding of a propeller's performance characteristics, making them essential for selecting the right propeller for a specific application.

Other options, while they may pertain to aspects of motors or propellers, do not specifically define the size measurement of a propeller itself and therefore wouldn't provide the accurate context for this particular question.