variable

a quantity that can change, often with a numerical value. For example, position and speed are variables.

value

the particular number (with units) that a variable may have. For example, 20 feet is a value.

speed

the distance an object travels divided by the time it takes.

average speed

the total distance divided by the total time for a trip.

constant speed

speed that stays the same. Moving at a constant speed means you travel the same distance each second (like perfect cruise control).

conversion factor

a ratio used to convert from one unit to another, such as from feet to meters.