What does isochor mean?
An isochor is a line or curve on a diagram or map that connects points of equal value. The term is especially common in thermodynamics, where an isochor may represent constant pressure or another specified property, and in geology, where it can join points of equal age or conditions. Isochors are used to display relationships within a system and to compare how other properties change while the selected value remains fixed. The name combines the Greek elements iso-, meaning “equal,” and khōros, meaning “space” or “place.” Although an isochor is conceptually similar to a contour, it is chiefly a scientific term. In English, it is most often pronounced with the first syllable stressed and the final syllable rhyming with “core.”
nounA line or curve on a graph or map connecting points of equal value. In physics, it commonly joins points having the same pressure or temperature; in geology, it marks points formed at the same time or under the same conditions.
- A line or curve connecting points of equal value, especially pressure or temperature.
- In geology, a line on a map joining rocks or structures of the same age or those formed under equivalent conditions.
"The isochor for the gas shows how its volume changes as pressure increases at constant temperature."
"Each isochor represents a constant temperature during the experiment."
"Geologists traced an isochor across the basin to map the boundary of a period of sedimentation."
The plural is formed by adding -s and is used for multiple equal-value lines or curves.
"Several isochors were drawn at different fixed temperatures."
An isochor turns a constant into a line: every point on it shares the same value, whether that value is pressure, temperature, or time.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does isochor come from?
Isochor was formed in the 19th century from Greek iso-, meaning “equal,” and khōros, meaning “space” or “place.” Its development followed the broader scientific use of Greek combining forms such as isobar and isothermal to name lines connecting points with a common property. The word is a cognate of isochronous, although the latter concerns equal timing or duration rather than equal values represented spatially.
Related word forms
How isochor is actually used
The term is primarily used in the physical and earth sciences. It is more technical than the general term "contour" and is often distinguished from a specific isotherm, isobar, or isochrone according to the quantity held constant.
Easily confused with isochor
An isochor connects points of equal value, whereas isochronous describes events that occur at equal times or at the same rate.
An isochor is a general equal-value line, while an isotherm specifically connects points of equal temperature.