What is negative energy?

Question

i mean realting to Casimir effect not the colloquilaism

Answer 1

stress

anger

jealousy

ignorance

...things like that

people need to find ways of releasing it.

Answer 2

For something like potential energy, you always have to measure it relative to something, some arbitrary zero point.  So if you have less energy than that, you have negative energy.  It is only the relative potential between one point and another that matters.

Answer 3

Colloquially: That which is generated by politics and the media. ;^)

Wikipedia has a good start -