What does unicellular mean?
Unicellular is a biological adjective meaning that something consists of only one cell. The term is used for organisms such as many bacteria, archaea, protists, and some microscopic algae, as well as for individual cells or structures viewed as self-contained units. It distinguishes single-celled life from multicellular organisms, whose specialized cells work together within a larger body. In scientific contexts, unicellular does not imply that the organism is simple in every respect: a single cell can contain complex networks of membranes, internal compartments, genetic material, and metabolic machinery. The word is also useful when discussing the basic structural unit of life, because it emphasizes that a cell can function as an organism in its own right. Its clearest use is therefore in descriptions of biological organization, where the contrast between one cell and many cells is important.
adjectiveHaving or consisting of a single cell; composed of one cell rather than multiple cells.
- Consisting of a single cell, as an organism or biological structure.
"A unicellular organism must perform all of its essential life functions within one cell."
"Most bacteria are unicellular organisms, although they may form communities within a biofilm."
"The laboratory examined how a unicellular organism responds to changes in temperature."
The smallest unit of life can also be an entire organism: unicellular beings pack every essential function into one microscopic cell.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does unicellular come from?
Unicellular was formed in English during the 19th century from the Latin-derived combining form uni-, meaning "one," and cellular, which is based on Latin cellula, meaning "small room" and ultimately giving rise to cell. The word belongs to a family of biological terms including cellular, multicellular, and intercellular. Its formation follows the same transparent pattern as many compound adjectives: a numerical prefix identifies the number of structural units, while the remaining element identifies the unit itself.
Related word forms
How unicellular is actually used
This is a formal scientific term used especially in biology. It is commonly used attributively before nouns such as "organism," "body," and "eukaryote."
Easily confused with unicellular
Unicellular means consisting of one cell, whereas multicellular means consisting of multiple cells.
Cellular describes something relating to cells in general, while unicellular specifically identifies something made up of one cell.