From lap timers to lugs, our extensive watch glossary will help you better understand any term you may be unsure about.

AnalogA traditional dial with a short and long hand pointing to the hour and minute. Numbers, markers, indices or Roman numerals encircle the dial and mark.

ApertureA small openening in the dial that displays information such as the date, day, month, or moon phase.

AppliqueNumerals or symbols applied to the dial.

ATMA measurement of pressure called an atmosphere. An atmospheric measure is the amount of air pressure at sea level that a watch can withstand. (1ATM = 1BAR = 10m - 33.3ft). No watch is 100% waterproof.

Common water resistance ratings:

  • 3 ATM = 30 meters/100 feet: Suitable for everyday use. No Swimming.
  • 5 ATM = 50 meters/165 feet: Suitable for short periods of swimming. No Diving or snorkeling.
  • 10 ATM = 100 meters/330 feet: Suitable for swimming and snorkeling.
  • 20 ATM = 200 meters/660 feet: Suitable for high-impact water sports and some diving.
  • Diver = 150-200 meters/500-660 feet: Suitable for scuba diving and passes ISO regulations.

BandThe straps or bracelets that wrap around the wrist. Metal bands are called bracelets. Leather, rubber, or fabric bands are called straps.

BezelThe outer ring encircling the dial that attaches the crystal to the watch case.

CaseThe frame that houses the watch mechanism.

Case BackA removable cover that allows access to the internal mechanism of the watch.

Clasp The hardware that fastens the band together; a buckle.

ChronographA stopwatch function that uses sub-dials to keep track of seconds.

ComplicationAny superfluous function added to a watch, such as a minute repeater, countdown timer, stopwatch, altimeter, asthometer, pulsometer, calendar, moon phase indicator, split second chronograph, power reserve indicator, or alarm.

Countdown TimerA chronograph function that measures how much of a preset period of time has passed.

CrownA button on the side of the case for adjusting the time and date. The button also winds many mechanical watches.

CrystalThe clear protective case over the top of the watch dial, usually a Plexiglass or mineral disc. Hardlex crystals, a heat-treated mineral crystal, and sapphire crystals are especially scratch-resistant.

DialThe face of the watch case that displays the timekeeping functions.

Dual TimeA display that shows two time zones on the dial. This feature can have either two dials, a sub-dial placed in the main dial, or an analog and digital display on the same watch.

End of EnergyA mechanical watch will indicate the end of its energy life with the second hand, which will jump every two, three, or four seconds.

End of LifeA quartz watch will indicate the end of its battery life with the second hand, which will jump every two, three or four seconds.

GasketMost water-resistant watches are equipped with gaskets that seal the case back, crystal and crown from water. Gaskets need to be checked every couple of years to maintain water resistance.

HackingA feature that stops the second hand when the crown is pulled out as far as it will go. This allows you to set the exact time.

JewelsVarious types of jewels are in the movement of mechanical and automatic watches. These jewels help reduce the friction and form of the bearing. A watch movement will usually have at least 17 jewels.

Lap TimerA chronograph function for timing multiple segments of a race. A lap timer can track each individual lap time as well as the total race time.

LugsThe hardware that connects the case to the watch band.

SkeletonA type of case design that displays the watch movement with an open dial or a clear crystal placed on the case back.

Sub-dialA small window or register with its own hands that is a subset of the main dial. Chronograph watches display multiple functions with three or four sub-dials.

Sweep HandA second hand on the automatic watch that "sweeps" around the dial in a smooth, continuous movement. The second hand of a quartz watch will click forward in second-long increments; a sweeping second hand moves in a continuous arc.

TachymeterA register on the bezel that measures distance covered over a specific period of time.