This post lists and defines lapse and its family of related words that pertain to a passage of time or to falling.
The words discussed below all derive ultimately from the Latin verb labi, meaning “fall,” “sink,” and “slip,” in addition to other related actions, by way of lapsus, meaning “falling” or “slipping” (figuratively or literally) or “passage of time” (from the sense of “gliding”).
Lapse, as a verb, originally pertained merely to that last sense, but it later applied as well to something becoming invalid or void and acquired the additional meanings of “commit a sin” or “fail to retain religious faith.” As a noun, lapse means “decline” or “fall,” or “interval,” “interruption,” or “termination,” or it may refer to a mistake due to forgetfulness or inattention, or to abandoning one’s faith.
The adjectival form is lapsed; the adjective labile once meant “prone to fail or fall,” but now it pertains to instability or propensity to change. (The adjective labial and other words pertaining to lips are unrelated.) Labefaction, meanwhile, is a rarely used word meaning “downfall” or “overthrow” in the sense of a weakening of civil order or moral principles.
When time goes by, it is said to elapse. That word was at one time also a noun, but lapse has superseded it.
In theology, several words with the root lapsarian pertain to various beliefs about the biblical account of the fall of humankind as told in the story of the Garden of Eden: postlapsarian (“after the fall”), prelapsarian (“before the fall”), sublapsarian (“under the fall,” which is also the translation of the synonym infralapsarian), and superlapsarian (“above the fall”).
The verb collapse (literally, “fall together”) means “fall” or “fall apart,” “break down” or “lose effectiveness or significance,” or “fold down” or “give way” and as a noun refers to any of these actions. Something that can be collapsed, generally limited to the sense of “fold down,” is collapsible, and that quality is called collapsibility.
When a body part falls or slips, it is said to prolapse (“fall forward”), and such an occurrence is a prolapse.
A relapse (“fall again”), meanwhile, is an instance in which symptoms of a disease that had abated recur, and the word also serves as a verb.
Lava is an unexpected cognate; the word describing magma, or molten rock, after it has surfaced from underground (in its molten state or after it has cooled and hardened) stems from lapsus by way of Italian. The adjective lavalike refers to something resembling the molten state.
Lapidary, referring to cutting of gems and stones, is an unrelated word derived from lapis, the Latin word for “stone.”
And allow me to add a couple more lapses you may have heard of...
Memory Lapse is when you know that you know something such as a person's name but just cannot think of it at the moment. Politicians are often known for having 'memory lapses'.
Time-lapse is a term usually used when talking about photography taken over a period of time such as to show how many lightning strikes there were overnight.
Oh, and don't confuse lapse with laps...the number of times a runner goes all the way around a running track, or a race car completes 'laps' around the racetrack or a swimmer goes from one end of a pool to the other.
Just to add to the confusion...
When you sit down, where your body bends is called your lap. Here is a child sitting on Santa'a lap.
...and, of course, everyone knows what a laptop is. It is a computer that is designed to sit on top of your lap.