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Main what? ETA who? A quick watch glossary.

Every group of nerds or hobbyists has their own set of terminology and watches are no different. What you will find here (hopefully) are some common watch terms; I’m not going to go into the deep nitty-gritty stuff and get all granular on your collective rears. The goal here is if I refer in a later post to something it won’t be confusing to those who may not have a deep knowledge of watches (which isn’t required to enjoy them, obviously). If a more detailed post is requested I’ll be happy to comply, but for now, let’s keep this high level. Let’s jump in, shall we, and review a few terms (with some nifty photos to illustrate).

Hand-Wind (or Manual-Wind) Movement – a watch that contains a hand wind movement pretty much works like it sounds: power to the watch is generated by turning (winding) the crown and which winds up the watch. Power is stored in a spring (the mainspring, see below) and the release of power is governed via a set of gears and wheels to end up driving the hands to keep the time. Many hand wound watches will keep running for around 40 hours (some more, some less) without being re-wound. More than that and they will stop time and need to be rewound and the time reset to be worn. Why in the world would one wear a hand wound watch then? Well, for a lot of people it’s simply the appeal of the beautiful, complex mechanical heart beating inside, as in the example below from Omega.

Automatic Movement – an automatic movement contains the same base parts as a hand wound with an additional piece called a rotor. The rotor is essentially a counterweight that lives on the back of the movement and freely spins as the watch is worn. This movement winds the watch and thereby delivers power again via the mainspring. As with a hand wind, power reserve will run normally around 40 hours and if left sitting untouched for that period it will stop. However occasional wear within its power reserve limit will still keep the watch running. Many people employ watch winders that take care of winding while the watch is not worn.

Quartz Movements – I would guess that quartz will be well known to most people. It’s what you will find in 90% of the malls across America in stores like Sears, JC Penny, Walmart, Target and the like; brands like Fossil and Armitron dominate this space with less expensive, battery-driven watches. And that’s the key behind quartz: the movement’s power source is driven from a battery and as with all batteries it will eventually drain of all power and need to be replaced. However, building a standard quartz movement requires far fewer moving parts than its mechanical counterparts, hence lower costs. On a quartz watch the seconds hand will move around the dial in one second jumps with a total of 60 in a minute, which differs greatly from mechanical watches which move several times a second which gives a much smoother sweep around the dial.

Quartz watches can come in a couple of other flavors, however, that use other technologies to power the watch rather than a battery. Citizen and Casio make a number of solar powered watches that literally draw their power from the sun instead of a battery (Citizen calls it Eco Drive and Casio, Solar). The power is stored inside the watch and released as with a battery to run the functions. Another version is the kinetic (Seiko) or mechaquartz or autoquartz (Swatch) which uses a rotor from an automatic watch to power a quartz capacitor which then powers the movement. No battery changes in these two types of quartz movements and generally longer life as well, although over time the capacitors can fail and will need to be replaced.

Bezel – the bezel on a watch is generally the ring around the outside of the crystal. It can be just a plain ring or have markings appropriate to the type of watch. Some sports watches will have a scale to determine distance over elapsed time (chronograph) and diver watches will have markings used to time dives and will actually rotate.

Chronograph – a chronograph is used to measure the elapsed time of an event. Quartz watches will often have a digital display for the chronograph via an LCD screen; mechanical watches will use sub-dials to track the time of the event. Most commonly on mechanical watches, the second hand for the time will be relegated to a sub-dial and the second hand for the chronograph will be placed front and center with the main hour and minute hands. This can allow for the use of markings on the bezel to assist with elapsed time tracking.

Crystal – this is the protective glass over the dial of the watch. Crystals come in a few different types, the main being sapphire (either natural or synthetic), mineral and plastic (acrylic). Sapphire crystals are the most expensive and for a good reason, as they are virtually scratch resistant. If you can help it sapphire is really the best way to go. Mineral crystals are next best behind sapphire and are a hardened glass that will resist some scratches but are not nearly as durable as sapphire. On the bottom rung are plastic or acrylic crystals which are just what they sound like, a piece of plastic. They are not scratch resistant, however often times scratches can be easily buffed out and the crystal made to look like new.

Display Back – rather than a solid piece of metal for the back of the watch, instead a crystal is used (either sapphire or mineral) to show off the watch’s movement.

GMT or UTC – both are acronyms for essentially the same thing and both indicate a popular second feature on some watches. GMT is short for Greenwitch Mean Time while UTC is Coordinated Universal Time. In discussion of time zones specifically both represent the time from which other time zones are measured in either + or – numbers. The Pacific time zone, for example, is GMT -8 (-7 during daylight savings) meaning that time kept by those in that time zone is 8 hours behind those in GMT. GMT and UTC can also indicate that a watch is capable of tracking a second (and sometimes third or fourth) time zone. Frequently this is done via an additional hour hand that moves around the dial in 24 hours, al la the Rolex GMT Master series of watches. There are some that will use an additional 12-hour hand like the Sinn 356 UTC.

ETA – ETA SA is a producer of mechanical and quartz watch movements – in fact, they’re at the top of the heap in this regard. They produce and sell movements to many major watch firms. They have purchased and own several other companies whose names are sometimes still used, such as Lemania and Valjoux.

Hacking Seconds (Hack) – this feature stops the second hand when you pull the crown all the way out to set the time. This allows one to more accurately set the time on the watch when using another source. You’ll frequently see this in action in WWII movies where pilots will synchronize their watches. They stop the second hand and all begin together so they are in sync.

Jewels – you wouldn’t wear these as earrings, as the synthetic rubies or sapphires in watches are used as pivots or hubs in certain moving parts. They are used as they can provide nearly frictionless surfaces for the delicate pieces. You’ll see a variety of numbers of jewels (and more does not necessarily mean better) from 17 and up in mechanical watches.

Lume – the term lume refers to the luminescence of the markers and hands on a watch for reading in low light conditions. Lume is charged by sunlight or artificial light and ideally would be visible in darkness for several hours.

Mainspring – This is the power source for mechanical watches, it literally is a tiny, coiled spring that after being tightened via winding slowly unwinds and releases its power.

Rotor – As mentioned above, this device, usually in a half-moon kind of shape, is used in automatic watches to wind the mainspring to provide power to the watch.

Screw Down Crown – To help the watch resist water some watches are fitted with a crown that threads into the case. Combined with gaskets this creates a seal that will help prevent water from entering, and damaging, the movement.

WR (Water Resistance) – This is the measure of how well a watch can withstand water and the pressures from being submerged. It is measured in meters (M) or feet (f) and sometimes both. If a watch has a WR rating of 30M it is considered safe from splashes and rain, but is not one you would want to take swimming. A 50M rated watch would be fine for swimming and 100M is considered safe for the former plus snorkeling and the like. When you reach 200M and above you begin to enter the realm of being capable of handing the pressures of scuba diving. There are watches rated for saturation diving as well and some with ratings of 1000M or 2000M!

I believe that covers many of the basic terms and concepts. If you feel I’ve left anything out please feel free to pop in a comment. I would be happy to add any additional terms to this post that others may feel will be helpful. I hope this was at least a little bit educational. Next time, a watch review!

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  1. Mal says:

    @ Doug Guerette; A Chronograph is essentially a stop watch

  2. Donnie Jones says:


    The word you are actually describing would be chronometer, i.e. officially certified chronometer. The definition that James provided is accurate for a mutitude of chronograph (function) equipped watches that are definitely not certified.

  3. Doug Guerette says:

    Your definition of CHRONOGRAPH is far different from mine. A Chronograph is a certified timepiece that keeps much more accurate time than most other watches and is certified to keep that accuracy by the maker and the Swiss certifying agency.

    What you’re describing is more akin to a stopwatch feature.

  4. Alex says:

    Thanks man, I’ve been scratching my head about what the heck those terms mean. Your post came right to the rescue!

  5. Gabrielle says:

    I’ve got a nerdgasm for you: how about engineering a 10,000 year clock?

    Fascinating project.

  6. Peter Whiting says:

    Clean, informative, concise and to the point: bit like a Patek Calatrava really.

  7. Speedmaster says:

    Fantastic post, thanks!

  8. christian says:

    I knew all of these after working for fine watches. Still it’s very nice (and slightly sexy?) to hear nerds talking about one of my favorite things.

  9. Pete says:

    I have a feeling your posts are going to end up being rather expensive for me!

  10. deb says:

    I found this to be wonderfully written and formatted for reading by just about anyone! I learned a couple of interesting details, too.
    And the exquisite images chosen for the contribution! Watch porn, pure and simple (in a good way)!