“Why do soldiers in movies always talk jargon on the radio? ‘Hotel two advancing one five klicks to grid sierra oscar niner fower BREAK ETA four zero minutes’ and all that.”

Radio telephones (voice radios) are very useful for communicating where people are moving around a lot and can’t access normal telephones. Aircraft pilots, mariners, police/fire services, and the military are all heavy users of voice radios.

Unfortunately, reception on voice radios can be very noisy, which makes it hard to understand what people are saying. On top of that, people have different accents and vocabularies, so even with perfect reception it can still be hard to understand what people are saying.

To overcome this, the people who use radios the most - mainly the military - have come up with radio procedures, which are standard ways of telling people things over a radio. Using standardised words, pronunciations, and phrases helps people communicate clearly over the radio, even if reception is bad or if the speakers come from different countries.

Letters

It is easy to confuse letters when heard over a radio, so full words are used to spell things out.

“License plate 141GGH” becomes “License plate one fower one golf golf hotel”.

The ‘standard’ translation of letters to words is the NATO phonetic alphabet, which is used by most English-speaking radio operators. The NATO alphabet starts “Alpha, Bravo, Charlie…" The words were specifically chosen so that none of the 26 words used sound similar to the others.

The NATO phonetic alphabet is well known in popular culture. Most people are exposed to it via radio chatter in TV and movies like The Bill (UK police drama) or Generation Kill (US military docudrama). The Bloodhound Gang song _Foxtrot Uniform Charlie Kilo _uses the phonetic alphabet to spell a rude word.

There are other phonetic alphabets: the “Able Baker” alphabet (“Able, Baker, Charlie, Dog, Easy, Fox…”) was used during WWII.

Numbers

The numbers 3, 4, 5 and 9 are pronounced differently by radio operators vs. everyone else.

“3” is pronounced “Tree”, with a hard ‘T’, because some speakers would otherwise pronounce it with an ’s’ - “Shree”.

“4” is pronounced “Fower”, to distinguish it from “for”.

“5” is pronounced “Fife”, because “Five” is easily confused with “FIRE”, the military command to fire weapons.

“9” is pronounced “Niner”, because ‘nine’ is too close to ‘five’. Historically, this also distinguished ‘nine’ from the German ‘nein’ (’no’).

Other bits of radio protocol

• When speaking decimal numbers, as in “3.141”, the decimal point is pronounced “DECIMAL”. That is, “Tree DECIMAL one fower one”. I don’t know why ‘DECIMAL’ is preferred over the more usual ‘POINT’.
• “Affirm” and “negative” instead of “yes” and “no”. Note that “affirm” is itself a modification of “affirmative”, because “negative” and “affirmative” both end in ‘ive’ and sound too much alike.
• When repeating information for clarity, the words ‘SAY AGAIN’ are used instead of ‘REPEAT’. I.e. “Turn right one seven degrees, SAY AGAIN, one seven degrees.” The word ‘REPEAT’ is not used, because ‘REPEAT’ is a command for artillery to fire another volley of shells!
• ‘SAY AGAIN’ can also be used to ask someone else to repeat a garbled transmission. For example, if you heard “All Hotel callsigns, Hotel Two, be advised Bruce Highway [garbled] near [garbled] due to flooding”, you might ask for a re-transmission with “Hotel Two, Hotel Seven, SAY AGAIN all after Bruce Highway.”

You don’t necessarily need to learn any of this for your daily life, but it may help you understand what the soldiers are saying in movies.

Further reading:

• Wikipedia - Procedure Word. (Interesting stuff.)
• Wikipedia - Voice Procedure. (Less interesting.)