6J

In mathematics and engineering, 6j denotes the pure imaginary complex number with real part zero and imaginary part six. The symbol j is used for the imaginary unit in many engineering disciplines instead of i, which is commonly used in pure mathematics. Thus 6j is equivalent to 6i in mathematical notation.

Algebraically, j^2 = -1, so (6j)^2 = -36. The complex number 6j has magnitude |6j| = 6 and argument π/2 (90 degrees); it lies on the positive imaginary axis in the complex plane. Its conjugate is -6j, and its multiplicative inverse is -j/6.

In practical contexts, 6j may appear as the imaginary part of a complex quantity, for example in impedance expressions Z = R + jX, where a term with X = 6 would be written 6j if R = 0. In programming languages such as Python, 6j is a literal for the complex number 0 + 6j.

As a numeric token, 6j is unambiguous only in contexts that distinguish complex numbers from other data. Outside mathematics and programming, 6j is seldom used as a standalone technical term and may appear as a string or part of a model code.