The E1cB elimination reaction is a type of elimination reaction which occurs under basic conditions, where the hydrogen to be removed is relatively acidic, while the leaving group (such as -OH or -OR) is a relatively poor one. Usually a moderate to strong base is present. E1cB is a two-step process, the first step of which may or may not be reversible. First, a base abstracts the relatively acidic proton to generate a stabilized anion. The lone pair of electrons on the anion then moves to the neighboring atom, thus expelling the leaving group and forming double or triple bond. The name of the mechanism - E1cB - stands for Elimination Unimolecular conjugate Base. "Elimination" refers to the fact that the mechanism is an elimination reaction and will lose two substituents. "Unimolecular" refers to the fact that the rate-determining step of this reaction only involves one molecular entity. Finally, "conjugate base" refers to the formation of the carbanion intermediate, which is the conjugate base of the starting material.