Number & MeasureGreek → English
Isometry
/aɪˈsɒmɪtri/noun
A transformation that moves every point of a space while leaving all distances between them unchanged.
The Greek roots
ἴσος
ísos
equal
μέτρον
métron
measure
Literally: “equal measure”
The story of the word
Slide a shape, spin it, flip it over, or do all three: every distance inside it survives, and that is an isometry. Geometers use it to define what congruence means without appealing to the eye. The gym sense comes from the same pair, since an isometric contraction loads a muscle without letting it change length.
- How it travelled
- Ancient Greek → scientific coinage → English
The same roots elsewhere
Other languages reached for exactly the same Greek pieces.
Same family
isoscelesisobargeometryisotope
In a sentence
Rotation about the origin is an isometry, so the triangle keeps its side lengths.
Every isometry of the plane is a rotation, a reflection, a translation, or a glide.