What is the term used to describe an organism made up of many cells?

An organism made up of many cells is referred to as multicellular. These organisms consist of a complex structure with different types of cells that can specialize to perform various functions. This specialization allows multicellular organisms to develop tissues and organs, leading to increased complexity and the ability to carry out more intricate biological processes compared to unicellular organisms, which are made of a single cell. Multicellular organisms include various forms of life such as plants, animals, and fungi, each exhibiting diverse cellular functions and interactions that allow for greater adaptability and survival in different environments.

The other terms refer to different characteristics of organisms. Unicellular describes organisms that consist of only one cell, while colonial refers to a group of identical cells living together but not forming a true multicellular organism. Single-celled, like unicellular, emphasizes the presence of only one cell in the organism.