Used in mathematics, Z is often used to refer to the set of integers.

The last and seldom used letter of the alphabet. Pronounced "zee" in the US and "zed" in Canada and other civilized places. (Observe: character Z in the Men in Black movie pronounced his name "zed".)

In graphing, the z axis is used to represent the third dimension.

The letter z is conventionally used to represent a complex number, of the form z = x + iy, where i is the square root of -1, making iy an imaginary number. It is also a shorter name for the left-wing alternative news source Z magazine.

In phonetics terms, the z sound in English is a voiced alveolar fricative: Unlike the s sound, which it otherwise resembles, we produce sound with our vocal cords when we say z; this give the sibilant a buzzy quality. The sound is produced between the tongue and the alveolar ridge.

The exact sound of a z varies from country to country, but like any letter most of the sounds it can stand for are at least somewhat related. In German, Maltese and some transliterations of Hebrew it's a sort of ts sound; it's the same in Italian, except when it's more of a dz. In modern Pinyin Chinese, z is used to represent the sound that earlier schemes rendered as ts or tz, so that Lao Tzu becomes Lao Zi or Laozi. This is an unaspirated alveolar sound, Excalibre tells me; like the other languages mentioned so far, it's an affricate, which is to say it's a fricative that starts with a plosive sound. In Japanese, it is dz in zu, but otherwise a lot like the English z. In Castilian Spanish it is pronounced as a th, but in the Spanish of Andalucia and South America (and also Basque) it is pronounced more like an s. In Scottish names like Dalziel and Menzies, the z takes the place of the extinct yogh, which stood for a y or a gh sound.

Ž in various languages (that's z with a hacek), zh, Chechnya's z with a line through it and the Russian Ж are all pronounced as a voiced palato-alveolar fricative, much like the s sound in the English pleasure and leisure and the French j. Other accented zs include ż and ź, both used in Polish.

With thanks to Gritchka for much of the information on phonetics.

Z (capital) is used in aviation, navigation and meteorology as well as by radio amateurs as an equivalent of UTC and stands for "zero longitude," that being the longitude of the Greenwich meridian. Pronounced Zulu since it's normally used within a context that requires use of the phonetic alphabet. Time thus formulated is called Zulu time.

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Zeta or Zita, sixth letter of the Greek alphabet. In older alphabets it was seventh and moved up to sixth after the digamma was dropped. Also serves as the Greek numeral 7.

Z is also the electrical symbol for impedance and to designate a device or circuit which has two or more components but is referred to as a whole, such as a parasitic tube grid supression device made of a resistor with a coil wired around it in parallel.

Z is a movie directed by Constantin Costa-Gavras about the military coup in Greece. It's an absolutely fantastic film, it's in my personal Top 5.

Music for the movie was written by the famous Mikis Theodorakis (who also did the music for Zorba The Greek). Unfortunately, since he was in exile (by the Greek fascists) during the making of the movie, Bernard Gérard directed the music.

Now with the story. A leftist organization organizes meetings against nuclear weapons and military bases in the country. After a meeting, the leader of the party (played by Yves Montand) is clubbed to death right in front of the cops and protesters. The police arrests the two men and tell everyone it was an accident (the driver was drunk).
The prosecutor is leading the investigations and as the plot moves on, we learn that almost everything was planned by the cops and military heads. They used a semi-secret right-wing organization called CROC for the murder.

Until the last minute, we think the left side is winning, discovering corruption everywhere in the army and government. I feel forced to tell the end, because it's what makes this movie so awesome. Finally, we have this journalist doing the epilogue. The murderers are sent to jail, the colonels, generals and military heads are lightly condemned, etc. Then the journalist says that two weeks before the new elections (the Left would clearly win), the army took over the government. Follows pictures of all the characters in the movie who were in the anti-nuclear and pacifist party. "this one died in a car crash", "jumped out of a window of the police station", "this one was exiled to the islands". Then we have the picture of the journalist, the voice changes to a woman: "Three years of jail for having secret official documents."
then follows a list of all things that were declared illegal in Greece (all true): mini skirts, Ionesco, pop music, Tolstoï, Albert Camus, and finally, the letter 'Z', because in Ancient Greek, it means "He is alive." As a matter of fact, the fascists in Greece really forbidden the use of the letter Z.
I've seen this movie like 5 times and I always start crying at the end. We think the 'good guys' will win over the corrupted army and police. No. Fascism wins.

I'm a true fan of Costa-Gavras. I think Z is simply his best movie and one of the best movie ever made. The original version is in French but I have the version with English subtitles, so you have no excuse to miss this piece of art.

A French chain of children's clothing shops. From 1986 to 1992, main sponsors of the eponymous professional cycling team (a successor to the long-lived Peugeot team and a precursor to the GAN and subsequently Crédit Agricole teams) which featured riders including Robert Millar, Pascal and Jérome Simon, Gilbert Duclos-Lasalle and Greg Lemond, who won the Tour de France in Z colours (blue, puce and yellow, since you ask) in 1990.

Z is a real-time strategy computer game for DOS (a Windows 95 version was later released) by the Bitmap Brothers, published by Virgin Interactive on the 31st July 1996.

It is very simple compared to most real-time strategy games: there is no building creation or placement. There are already factories placed on the map, which you can take over and use to build such things as jeeps and train men, and radar.

The map consists of 12 areas, in a 3x4 grid. Each of these areas contains a flag, which you must capture in order to hold that area. While you are holding an area, you have control of any factories or other buildings which may be inside that area.

The AI tends to be rather stupid at times, preferring to blow up terrain rather than take the faster route around it.

Another fun feature of the game is the ability to snipe the drivers out of vehicles, allowing your own soliders to take these vehicles over. The sound clips are rather funny too, although the novelty quickly wears off.

It is a very fast-paced and fun game, although too simple for some peoples tastes. The hilarious FMV movie clips, featuring two incompetent, lazy and idiotic robots, easily make up for any shortcomings of the game itself.

There is a sequel called Z: Steel Soldiers.

Z (pronounced "Zed" in this context) is a language used in software engineering for formally describing systems of all kinds, especially information processing systems, the most common example being computer programs.

Z is not a programming language. It is much closer to a markup language such as HTML and XML. It describes the system in terms of inputs, outputs and data types. It relies on a lot of math, especially logic, calculus and set theory, with the aim of a Z specification being to produce a description of the system that can be proven mathematically correct: in other words, you can prove that your program will always behave in a way that is precisely defined and totally predictable, if not always the way you wished/designed it to.

Z is a funny language to look at: boxes and lines and strange mathematical-notation arrows for functions, surjections, injections and bijections abound. It looks like math, and as such it cannot be easily typed straight into a computer using an ordinary keyboard. Instead, using backslash as an escape symbol, a variety of codes are used to represent the various mathematical symbols. These can be interpreted by LaTeX to "draw out" a more human-readable version of the specification.

Z cannot be compiled, because it's not a programming language. However, an interpreter called fuzz can be used with LaTeX to perform type checking. However, this simply ensures that the specification is valid Z and that data types are used consistently: the specification could still be wrong or nonsensical.

Z is a scale used in model railroading. Created by Märkin/Marklin, a German model train company in 1972. Z scale is 1:220. Current major z scale manufacturers are Märklin, Micro-Trains, Rogue, and others.

The symbol on an engine-order telegraph (EOT) used to designate the order "all stop".

Z, the band, was formed in the early 90's by Dweezil Zappa and Ahmet Zappa with Zappa stalwarts Mike Keneally and Scott Thunes. Shampoohorn was released in 1994, and was loved by guitarists and some critics but was not promoted much at all. Music For Pets followed in 1996 to similar response.

Originally consisting of the Zappa brothers and some FZ alumni, the drummer seat was in a state of constant flux. While touring pre album, the tour drummer, Joe Travers became the official drummer, and personality conflicts determined that ultimately Zappa alum Thunes would not remain with the band. A friend of the drummer, Bryan Beller joined up and remained until the band imploded.

The band existed in a very difficult time in the Zappa family, as Frank Zappa was dying of cancer. This led to numerous delays in album releases and supporting tours, neither of which helped the promote the band. The excessive downtime resulted in bassists Beller and guitarist Keneally working up a side project that ultimately got them fired.

Reportedly, there are dozens of songs that were recorded during the many delays in album release that have yet to see the light of day. A special box set with a video and a CD of outtakes was (and probably still is) available through Barfko-Swill, the Zappa distribution arm. One legendary track, Purple Guitar, showed up on Dweezil's 2000 solo album Automatic. All of the Z players appear on Automatic.

Albums:
Shampoohorn (1994)

Music for Pets (1996)