What does pilus mean?
A pilus is a very small, specialized unit of force equal to 10^-12 newton, or one trillionth of a newton. It is chiefly encountered in scientific writing and is valued mainly for expressing forces too tiny to describe conveniently with ordinary units. The plural is pili. In biological and Latin-derived contexts, pilus also denotes a hair or a microscopic hair-like structure, such as a projection from a surface. This second sense belongs to technical vocabulary rather than general everyday English. Although the scientific and biological senses differ in subject matter, they ultimately share the same Latin foundation: pilus, meaning “hair.” The word is therefore especially useful to readers of older physics texts, specialist scientific papers, zoological descriptions, and works discussing structures named by analogy with hair.
nounA pilus is an extremely small unit of force equal to 10^-12 newton. In biological and Latin-derived contexts, it can also mean a hair or hair-like structure.
- An obsolete or specialized unit of force equal to 10^-12 newton.
- In biological usage and Latin-derived terminology, a hair or a hair-like structure.
"The researchers measured a repulsive force of several pili between the microscopic surfaces."
"The instrument was sensitive enough to detect forces measured in pili."
"Each pilus on the leaf surface contributed to the insect's ability to remain attached."
The plural is used for both the unit of force and hairs or hair-like structures.
"The model predicts that each surface can sustain forces of several pili."
A force of just one pilus is a trillionth of a newton, yet the name comes from the Latin word for a single hair.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does pilus come from?
The English word comes from Latin pīlus, meaning “hair” or “a hair.” Its use as a unit of force preserves that imagery, suggesting a quantity as minute or fine as a hair. The term later became established in scientific measurement for the billionth of a billionth of a newton.
How pilus is actually used
The force unit is uncommon outside specialist physics literature. The meaning 'hair' belongs chiefly to biological terminology and to Latin-derived usage, where the plural is pili.