“Incommensurate” is best understood by contrasting it with its opposite, “commensurate.” Something that is commensurate is corresponding in size, extent, amount, or degree, or it’s equal in measure. The prefix “in-” means it’s the opposite of the root word, so “incommensurate” is applied to something that doesn’t match up, or that’s inadequate or disproportionate in some way. A small snack is incommensurate with a grand all-you-can-eat buffet, for example. Feelings are also often described as incommensurate. A toddler might have a meltdown that seems incommensurate with the idea of going down for a nap.