Partitive Structure with Uncountable Nouns

To count or quantify an uncountable noun we use a unit of measurement - a measure word. For example, we cannot usually say “two breads” because “bread” is uncountable. So, if we want to specify a quantity of bread we use a measure word such as “loaf” or “slice” in a structure like “two loaves of bread” or “two slices of bread”. We call this structure a partitive structure.

We can use the same uncountable noun in different partitive expressions with different meanings. For example, a loaf of bread and a slice of bread are partitive expressions with different meanings. A loaf of bread is what we call a whole unit of bread that we buy from a baker. A slice of bread is what we call a smaller unit of bread after it has been cut from a loaf. 

Here are some more examples:

• Don't forget to buy a bag of rice when you go shopping.
• Can I have one cup of coffee and two cups of tea.
• The police found some items of clothing scattered around the floor.
• I need a truck that will take at least three pieces of furniture.
• You'd think a tablespoon of honey would be more than enough.

See also in Vocabulary:

• List of common measure words
• List of partitive expressions with uncountable nouns - and example sentences