State the term- - GDP is a flow

Lastly, note that GDP is a flow variable and not a stock variable. By a flow variable we mean a variable which is measured in something per unit of time. If you fill a bath tub you may fill it at 40 liters per minute- a flow - whereas the tub itself may comprise 200 liters - a stock. In the similar way, income is flow (you may make 9 euro per hour) whereas amount of money you have in your bank account is a stock (you would never claim that you have 2400 euro "per month" in your account - you have 2400 euro period).