The phrase "pieces of furniture" is plural. The word "pieces" is the plural form of "piece," and "furniture" is an uncountable noun, meaning it does not have a plural form. When you refer to "pieces of furniture," you are talking about multiple items or units of furniture. For example:

• Singular: "This piece of furniture is beautiful."
• Plural: "These pieces of furniture are beautiful."

In the singular example, "piece" refers to one item of furniture, while in the plural example, "pieces" refers to multiple items. The word "furniture" remains the same in both cases because it is uncountable.