Can these words be used interchangeably or are there any rules relating to their usage? Dictionaries don't help much. Which of these three words would best fit the following sentences?
- The ... (amount?) of water used for cleaning has decreased from 20 litres per washing to 10 litres.
- The line represents the ... (quantity?) and type of food babies require.
- The ... (volume?) of global trade in merchandise has been increasing rapidly.