Libido

I think it’s interesting that it is debated whether psychic energy is real or not, yet here it is in Webster’s Dictionary being used to define libido:

Libido:  noun \lə-ˈbē-(ˌ)dō also ˈli-bə-ˌdō\

: a person’s desire to have sex

: instinctual psychic energy that in psychoanalytic theory is derived from primitive biological urges (as for sexual pleasure or self-preservation) and that is expressed in conscious activity