Loop is a common English noun and verb, while loupe is a French word, rarely used in English, where it has two rather special, narrow, meanings.
A loop (noun) is a shape or path similar to a circle, and to loop (verb) means either “to move in a loop,” or “to use a loop,” such as a loop of thread, for example while knitting. But a loop is not exactly a circle.
A loop can be any line or path that surrounds (goes around) something, such as a hiking path around a lake:
There is a trail that makes a loop around the lake.
A loop can also mean a circle within a larger path. Additionally, loop has other unique, metaphorical, uses:
- To be thrown for a loop means to be surprised or disoriented
- To be out of the loop means to be disconnected from a network, such as socially
- To loop through instructions means to repeat a sequence of instructions
- A loop of instructions in computer programming, such as a “for-next” loop
- A tape loop is a piece of a recording (audio or video) made to repeat over and over
- A loop-the-loop is a kind of amusement park ride:
Finally, a person can be loopy, which means a little crazy, or intoxicated.
The word loupe, on the other hand, is not even English, but rather a French word that is known by many English speakers, but not often used. It is best known from the French word loupe-garou, meaning “werewolf,” a creature from folklore (and horror movies) –someone who turns into a wolf under the full moon.
The other meaning of loupe in English is “a small magnifying glass used by jewelers;” however, this word is rarely used outside of this context—it’s considered jargon, and few English speakers are likely to know it.