This is the 4566th most frequent Polish word.
litrów
"Liters" (plural form of the unit of volume "liter").
The word 'litry' in this sentence is the plural form of 'liter,' used to quantify milk, in its accusative case due to its complement properties.
Kupiłem dwa litry mleka w sklepie.
I bought two liters of milk from the store.
Here, 'litrów' denotes the genitive plural form of 'liter,' used to express the capacity of the tank.
Pojemność zbiornika wynosi pięć litrów.
The capacity of the tank is five liters.
In this case, 'litra' is in its singular genitive form, complementing the numerical phrase 'półtora' to measure an amount of water.