number axis

The real line is a line with a fixed scale so that every real number corresponds to a unique point on the line.

The term "real line" has a number of different meanings in mathematics. Most commonly, "real line" is used to mean real axis, i.e., a line with a fixed scale so that every real number corresponds to a unique point on the line. The generalization of the real line to two dimensions is called the complex plane. The term "real line" is also used to distinguish an ordinary line from a so-called imaginary line which can arise in algebraic geometry. Renteln and Dundes give the following (bad) mathematical jokes about the real line: Q: What is green and homeomorphic to the open unit interval? A: The real lime.

abscissa | Argand diagram | complex plane | imaginary axis | imaginary line | line | moat-crossing problem | real axis

middle school level (California grade 7 standard)