What term is used to describe cells that lack a nucleus?

The term used to describe cells that lack a nucleus is "prokaryotic cells." Prokaryotic cells are characterized by their simplicity and smaller size compared to eukaryotic cells. They do not have membrane-bound organelles, which includes the absence of a true nucleus. Instead, their genetic material is typically found in a single circular strand of DNA located in a region called the nucleoid.

In contrast, eukaryotic cells, which are more complex and larger, contain a defined nucleus that houses their DNA as well as various organelles like mitochondria and endoplasmic reticulum. The other options, plant cells and animal cells, both belong to the eukaryotic category and therefore do possess a nucleus. Understanding these distinctions is crucial for differentiating between the two major types of cells in biology.