You might be familiar with “subliminal,” meaning “inadequate to produce a sensation or a perception” or “existing or functioning below the threshold of consciousness.” Subliminal messaging, for example, involves signals that are so imperceptible, a person will not consciously notice them. “Liminal” strips away the “sub-” and becomes “barely perceptible or capable of eliciting a response.” A butterfly landing on your head would be a liminal sensation. Both “liminal” and “subliminal” come from the Latin “limen,” meaning “threshold,” with the prefix “sub-” meaning “under, below.” The other usage of “liminal” refers to the threshold between boundaries — being in a liminal state means to be between one situation and another.