a quantity that can change, often with a numerical value. For example, position and speed are variables.
the particular number (with units) that a variable may have. For example, 20 feet is a value.
the distance an object travels divided by the time it takes.
the total distance divided by the total time for a trip.
speed that stays the same. Moving at a constant speed means you travel the same distance each second (like perfect cruise control).
a ratio used to convert from one unit to another, such as from feet to meters.