The collective noun for furniture is “furniture” itself. Unlike many nouns that have specific collective terms, furniture is classified as an uncountable noun, which means it doesn’t have a distinct plural form and doesn’t need a collective noun to represent a group of items.
When discussing multiple pieces of furniture, we typically reference them as “pieces of furniture” or simply “furniture.” For example, one might say, “I bought several pieces of furniture for my living room,” rather than inventing a particular term like a “set” or a “collection” of furniture. This is very common in English, where certain categories of items don’t adhere to the conventional rules of pluralization.