Inside the World of Travel: How to get from Alpha to Bravo without being a Charlie - cracking the code of tourism can be quite a journey in itself.
ON MONDAY, I checked out because I wanted to leave. Next, I checked in because I wanted to leave. Then I checked in because I wanted to stay. And, later that evening, having earlier been a runner, I discovered I was, in fact, a Billy.

This short journey, from the Ibis Hotel at Luton airport to the Hostal Ritzi in Palma de Mallorca, demonstrates how curious the language of travel has become. Can there be any other industry where the English language is so strangely distorted?

The vocabulary of tourism is full of terms that confound logic, or which have strayed well away from their original meaning. The same phrase, "check in", has separate meanings depending on whether you are registering for a hotel or about to board a flight. Resting snugly on this pile of linguistic ambivalence is a sack of jargon like the baggage that practitioners in every industry carry.

Today, in this A to Z of travel from Abta to Zulu, you can start to decipher the code the travel industry is using about us, and unravel terms that mean the exact opposite of what they say: to help you get from Alpha to Bravo without being a Charlie:

Abta: not strictly the Association of British Travel Agents. Abta combines an Association of Some British Tour Operators (the people who put the holidays together) and Some British Travel Agents (the people who try to flog said holidays). This is not a comfortable situation for a trade body.

Adult: a person older than anywhere between seven and 19, depending on the rules of the holiday company or travel operator.

Airside: the portion of an airport terminal beyond the security check. All-inclusive: a holiday where not everything is included.

Billy: holiday rep slang for tourist. British Airways: sometimes, the UK's biggest airline; at other times, one of the 22 other airlines whose services masquerade as BA flights (see also code-sharing). Check in: at a hotel, to stay; at an airport, to leave.

Code-sharing: the codes are not shared; the flight is. Indeed, the point of this aviation practice is that a single aircraft carries two or more flight numbers: Virgin Atlantic's flight VS15 from Gatwick to Orlando doubles as Continental's flight CO4415. You might think you're boarding a British Midland flight at Edinburgh for the short hop to Heathrow, but it is also posing as an Air Canada and Lufthansa flight. The right phrase is "plane-sharing".

Confirmed (as in plane tickets): not confirmed. Because of their practice of overbooking, most airlines do not guarantee you will get on the flight.

Departure lounge: a term that has strayed from travel parlance into everyday language (as in "He's in the departure lounge", to describe a relationship that is about to end). Similar escapees: "excess baggage", and "pilot error". Direct: (as in flights), usually indirect, ie touching down at least once along the way. Duty-paid store: since the ending of duty-free privileges within the EU, just like any other shop, except at Luton and Palma airports where domestic passengers and normal people are not allowed to buy.

Economy (as in tickets): not very economical; an airline's published economy fare is often absurdly high. Discounted tickets are usually much cheaper. But whichever you buy, you'll end up flying in the same seat. Equipment: aircraft; on a flight schedule, the code EQV means "equipment varies", ie the airline isn't absolutely sure which plane it will use.

First (as in railway classes): second, at least on Midland Mainline, which offers a "Premier" service designed to be better than first. Fly (as in "I flew from London to Paris on BA, then flew to Dakar on Air France"). No, you didn't; you were flown.

JMC: Thomas Cook. The initials are those of his son, John Mason Cook, and will be used for the group's package holidays from next year.

Landside: the part of an airport terminal before the security check.

Minor (in the sense of changes to holidays): major. According to Britain's biggest holiday company, Thomson, a "minor" change in your holiday could mean a 12-hour change in departure time; Cosmos says moving your departure airport 60 miles from Gatwick to Luton is a "minor" alteration. The result: you get no compensation.

Non-stop: one stop. Trains, boats and planes stop when they reach (or fail to reach) their destination.

Pax: passengers. Runners: pax who arrive after the official check-in time, but are allowed to try to catch the flight. This often results in a comical performance as flustered flyers struggle to get their luggage landside to airside and on to the flight. Also known as HAGs ("have a go"s).

Seat-only: more than a seat. This is a ticket on a charter flight where you can expect a drink and a meal, and a plane in which the seat can travel. Tax: when applied to flight tickets, often not a tax at all but the charge levied by the airport on the airline. Abta (see above) is complaining about this practice. TOD: not a traveller going solo, but "ticket on departure", a service used by late-bookers to get their travel documents at the airport. Increasingly, holiday companies are imposing a fee of pounds 10-pounds 25 for the privilege.

Tourist: almost always perjorative. "Tourist" class means the cheap seats on planes. "I'm a traveller, you're a tourist" is the bray of the backpacker. Calling a place a "tourist trap" (as Volendam is described in the story above) is not a commendation. Last year, BBC2's Travel Show (not Tourist Show, note) included a feature about popular tourist attractions that was called simply "The Trap".

Traveller: tourist (or, in the New Age sense, a person who resides in a battered bus beside the A30 in Wiltshire and rarely travels anywhere). Ultra all-inclusive: a holiday where more is included than on a regular all-inclusive, but still not everything. Zulu: Greenwich Mean Time.