What is the X in X-mas?
endergonic end·er·gon·ic (ěn'dər-gŏn'ĭk)
Of or relating to a chemical reaction that absorbs energy and therefore cools its surroundings.
Relating to a chemical reaction that requires the absorption of energy. The production of sugars by plants during photosynthesis is an endergonic reaction, where sunlight provides the necessary energy. Compare exergonic.