What does amoeba mean?
An amoeba is a single-celled microscopic organism belonging to a group of simple life forms known as protozoans. Its defining feature is its shapelessness: it has no fixed form and instead moves and feeds by extending temporary projections of its cytoplasm, called pseudopodia, which flow outward to pull the cell along or engulf food particles. The name derives from the Greek word 'amoibē', meaning change, reflecting this constant shifting of shape. Although biologists now classify amoebas across several unrelated groups rather than as a single taxonomic category, the term remains widely used to describe these flexible, primitive cells. Beyond biology, 'amoeba' is sometimes employed figuratively to describe something rudimentary or undeveloped, such as an idea or institution in its earliest, most basic stage. The plural may be written as 'amoebas' or, following Latin convention, 'amoebae'. Familiar both from school science lessons and from popular accounts of waterborne parasites, the amoeba has become shorthand for life at its simplest and most adaptable.
nounA single-celled microscopic organism that moves and feeds by means of temporary projections of its cytoplasm called pseudopodia; also, more broadly, any simple single-celled organism.
- A single-celled microscopic organism that moves and feeds using pseudopodia (temporary projections of cytoplasm), especially one of the genus Amoeba.
- Any simple, primitive single-celled organism, used more loosely in biology.
- Figuratively: something extremely simple, primitive, or lacking development (e.g. 'a political system still at the amoeba stage').
"Under the microscope, the amoeba extended its pseudopodia and slowly engulfed its prey."
"Under the microscope, the amoeba extended its pseudopodia and slowly engulfed its prey."
"Critics dismissed the early draft as little more than an amoeba of an idea — formless and barely alive."
Both plurals are correct: 'amoebas' follows normal English pluralisation and is now more common, while 'amoebae' preserves the Latinate form and is often preferred in formal or academic writing.
"Several amoebas were visible in the drop of pond water."
The word 'amoeba' comes from Greek 'amoibē', meaning 'change' — fitting for a creature so shapeless that scientists once argued over whether it was even an animal.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of amoeba
The word 'amoeba' was coined in the mid-19th century from the Greek 'amoibē', meaning 'change' or 'alternation', chosen because of the organism's constantly shifting shape. It entered scientific vocabulary through German naturalist usage before being adopted into English. The Greek root 'amoibē' is related to words conveying exchange or transformation, and cognates sharing this root include terms built on the same Greek stem denoting change or formlessness, such as 'amorphous'.
Related word forms
How amoeba is actually used
Plural is either 'amoebas' (anglicised) or 'amoebae' (Latinate); both are accepted, with 'amoebas' now more common in everyday English. The spelling 'ameba' is a common US variant. In figurative use, the word carries a mildly derogatory connotation of primitiveness or lack of sophistication.
Easily confused with amoeba
Anaemia is a medical condition involving a deficiency of red blood cells or haemoglobin, whereas an amoeba is a single-celled organism.