# Symbols:J

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### Imaginary Unit

$j$

Used in physics and engineering to denote the imaginary unit.

This is to relieve confusion with electric current, often denoted with the letter $i$.

The $\LaTeX$ code for $j$ is j .

### Unit $y$ Vector

$\mathbf j$

Used to denote the unit vector in the positive direction of the $y$-axis.

The $\LaTeX$ code for $\mathbf j$ is \mathbf j .

### Unit Quaternion

$\mathbf j$

Used to denote one of the units in the system of quaternions.

The $\LaTeX$ code for $\mathbf j$ is \mathbf j .

### Electric Current

$\mathbf J$

The usual symbol used to denote an electric current when it is necessary to treat it as a vector quantity is $\mathbf J$.

Its $\LaTeX$ code is \mathrm J .

### Joule

$\mathrm J$

The symbol for the joule is $\mathrm J$.

Its $\LaTeX$ code is \mathrm J .

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