# Differentiating esters from glycosidic linkages

What exactly is the difference between an ester linkage and a glycosidic linkage? I know both release a molecule of water, but what is the difference? Is it simply which types of monomers are involved in the bond?

Technically speaking, glycosidic linkage is just a special case of acetal or ketal linkages; that is the correct name for the functional group $\ce{R^1O-CR^2R^3-OR^4}$ — acetal if either $\ce{R^2}$ or $\ce{R^3}$ is a hydrogen, otherwise ketal if both are carbons. ($\ce{R^1}$ and $\ce{R^4}$ must be carbon-based or we are dealing with hemiacetals/hemiketals/hydrates.) Examples of ketals for glycosidic linkages exist.
(And technically, ortho-esters exist, too, in which the linking carbon is bound to three $\ce{OR}$ groups. But these are very rare and special cases, even though they even exist in natural products such as tetrodotoxin.)