aid for the hard of hearing Local loop, the physical link in telephony that links the customer premises to the telephone company (telco) Loop device, a Unix device node that allows a file to be mounted as if it were a device LOOPS, the object system for Interlisp-D Mathematics Loop (algebra), a quasigroup with an identity element Loop (graph theory), an edge that begins and ends on the same vertex Loop (topology), a path that starts and ends at the same point, possibly reduced to a single point Sports Loop, a type of playboating maneuver Aerobatic loop, a type of aircraft aerobatic maneuver Loop (cricket), an aspect of bowling in cricket Loop jump, a figure skating jump Loop, a type of offensive shot in table tennis Roller coasters Loop (roller coaster), a basic roller coaster inversion Pretzel loop, a roller coaster element Transportation Loop (Amtrak train), a discontinued Amtrak train The Loop (CTA), a rapid transit section bounding Chicago's Loop neighborhood Loop, underground public transportation system of The Boring Company in Tesla cars, including a proposed DC-to-Baltimore system Balloon loop, a section of track that allows reversal of direction without stopping Circle route, a public transport route that travels around and connecting the peripheral zones of an area. Loop line (railway), a branch line that deviates from a direct route and rejoins it at another location Loop route, a main route or highway that forms a closed loop Passing loop, a short section of track that allows trains to pass on a single track route Ring road or loop, a main route or highway that encircles a town or city Spiral (railway), a section of track that allows a train to climb a steep hill Other uses Loop (biochemistry), a flexible region in a protein's secondary structure Loop (education), the process of advancing an elementary school teacher with his or her class Loop (knot), one of the fundamental structures used to tie knots Loop, a cul de sac Loop, a type of fingerprint pattern See also The Loop (disambiguation) Loophole Looping (disambiguation) Loopy (disambiguation) Loupe, a small magnifying glass used by jewelers, watchmakers, and other precision craftsmen Circle Cycle (disambiguation) Cycle graph Electronic circuit Hoop (disambiguation) Inner loop (disambiguation) Line echo wave pattern (LEWP) Möbius strip Ring (disambiguation)