# ! Undefined control sequence in equations [closed]

The code:

$$\frac{E_porous}{E_bulk}= \frac{(1 - P_{o})^2}{1+2P_{or} - 3\nuP_{or}}$$

and the error: ! Undefined control sequence. 1+2P_{or} - 3\nuP {or} l.265 ...ac{(1 - P{o})^2}{1+2P_{or} - 3\nuP_{or}}

## closed as off-topic by Raaja, egreg, Phelype Oleinik, Andrew Swann, TiuriFeb 11 at 11:09

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• The macro \nuP is not defined in any standard class. You probably meant to write \nu P. – alephzero Feb 11 at 10:42
• @Yasamin insert a space between \nu and P. – Raaja Feb 11 at 10:42
• I'm voting to close this question as off-topic because it is solved in comments. – Raaja Feb 11 at 10:43
• Thanks all of you. – Yasamin Feb 11 at 10:52