What does abscissa mean?
An abscissa is the horizontal coordinate of a point in the Cartesian plane — the value that tells you how far, and in which direction, the point lies from the vertical axis. In the familiar ordered pair (x, y), it is simply the x-value, while its partner, the ordinate, supplies the y-value. Together they fix a point's position exactly. The term belongs chiefly to mathematics and the sciences, appearing in textbooks, graphs, and technical papers where precision matters; everyday speech prefers "x-coordinate." Its plural may be written either "abscissas" or, in more formal usage, "abscissae," following Latin convention. What makes the word memorable is its origin: it derives from the Latin abscissa, meaning "cut off," reflecting the older geometric practice of cutting a line segment off from an axis to measure it. Knowing the term is useful for reading coordinate geometry with confidence and for understanding the vocabulary behind graphs and plots.
nounThe horizontal coordinate of a point in a Cartesian plane, measured as its distance from the vertical (y-)axis along a line parallel to the horizontal (x-)axis. In the ordered pair (x, y), the abscissa is x.
- The x-coordinate of a point in a Cartesian coordinate system: its signed distance from the y-axis measured parallel to the x-axis.
- More broadly, the independent variable or first element in an ordered pair or graphed relationship.
"To plot the point, first locate its abscissa on the horizontal axis and then move vertically to the corresponding ordinate."
"On the graph, each data point's abscissa records the year and its ordinate records the population."
"When the abscissa is negative and the ordinate positive, the point lies in the second quadrant."
Both plurals are accepted; "abscissae" follows the Latin pattern and appears more often in formal mathematical writing, while "abscissas" is the natural English plural.
"Plot the abscissae of all three points before drawing the curve."
"Abscissa" comes from Latin for "cut off" — because in classical geometry, the line was literally cut off from the axis at that point.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of abscissa
Abscissa comes from Latin abscissa (linea), meaning "a cut-off (line)," from the verb abscindere, "to cut off," formed from ab- ("away") and scindere ("to cut"). It entered English mathematical usage in the 17th century, when analytic geometry was being developed following Descartes' work. It shares this root with English words such as "abscission" (the act of cutting off) and "abscise," all tracing back to the same Latin verb.
Related word forms
How abscissa is actually used
A technical term used mainly in mathematics, physics, engineering, and education. It is almost always paired with its counterpart "ordinate" (the y-coordinate). The plural is both "abscissas" and the Latinate "abscissae"; the latter is common in formal mathematical writing. Outside technical contexts the plain terms "x-coordinate" or "horizontal coordinate" are more widely understood.
Easily confused with abscissa
The ordinate is the vertical (y-)coordinate of a point, whereas the abscissa is the horizontal (x-)coordinate.