What word refers to any living thing?

The term that refers to any living thing is “organism.” An organism is defined as an individual living entity that can carry out life processes independently. This encompasses a wide range of life forms, including plants, animals, fungi, and microorganisms.

The other terms have more specific meanings. For example, "entity" is a broader term that can refer to anything that exists but does not specifically denote a living thing. "Life form" is a term that can also refer to living organisms but is less commonly used in scientific contexts compared to "organism." "Biotic factor" refers specifically to the influence of living organisms within an ecosystem, making it context-specific rather than a general term for any living thing.

Thus, "organism" is the most accurate and universally accepted term to denote any living thing.