Military Alphabet · Letter X
X in the Military Alphabet: X-ray
Code word, pronunciation, history, and how to use it when spelling out loud
In the military alphabet, the letter X is X-ray, pronounced ECKS-ray. It is the NATO/ICAO code word for X — the same word radio operators have reached for since the 1920s.
Official tables differ on the hyphen: NATO prints the code word as Xray, one word, so it cannot be read as two, while ICAO publications keep the hyphenated X-ray.
Why "X-ray"?
When Wilhelm Röntgen discovered a new kind of radiation in 1895, he named it the X-ray, borrowing the mathematician's x for an unknown quantity. Within a generation the term was understood worldwide, which made it a natural pick for a letter that begins few common words in any of ICAO's working languages. The RAF adopted X-ray in 1924 and the Able Baker alphabet kept it. ICAO's 1951 draft experimented with Extra, but testing sent the committee back to X-ray for the final alphabet of 1956.
X Across Spelling Alphabets
| Alphabet | Word for X |
|---|---|
| NATO/ICAO | X-ray |
| LAPD | X-ray |
| Western Union | X-ray |
| German (Classic) | Xanthippe |
| German (DIN 5009:2022) | Xanten |
| French | Xavier |
| Spanish | Xilófono |
| Italian | Xeres |
| Able Baker (WWII, historical) | X-ray |
| RAF 1924 (historical) | X-ray |
X-ray is one of the oldest words in the alphabet, in military use since the RAF list of 1924. Its only interruption came between 1951 and 1956, when ICAO's draft alphabet tried Extra before the familiar word was restored.
X-ray in the Field
The US Navy still sets material condition X-ray — the most relaxed of its three damage-control readiness states, ahead of Yoke and Zebra — aboard ships in port. British special forces gave the word a harder job: during the 1980 Iranian Embassy siege in London, the SAS labeled the gunmen X-rays and the hostages Yankees, a convention that persists in hostage-rescue work. On an ordinary phone call, X-ray simply anchors one of the rarest letters in English when a serial number or postcode has to survive a bad line.
"X as in X-ray" on the Phone
The registration ends in X9 — X as in X-ray, then the digit nine.
More on spelling out names and codes call-side in the phone spelling guide, and every letter's "as in" word is on the letters-as-words page. To convert whole words instantly, use the free military alphabet translator.
ONE TO REMEMBER
The US Navy's three material conditions — X-ray, Yoke, Zebra — are a fossil of alphabet history: X-ray survives in today's alphabet, while Yoke and Zebra are holdovers from the WWII Able Baker list.
Frequently Asked Questions
What is X in the military alphabet?
X is X-ray in the NATO phonetic alphabet, the international spelling alphabet used by NATO, civil aviation, and maritime radio since 1956.
How do you pronounce X-ray?
ECKS-RAY, with the emphasis on the first syllable, exactly as the medical term is spoken.
Has X ever been anything other than X-ray?
Only briefly. ICAO's 1951 alphabet used Extra, but the 1956 revision restored X-ray, which had served in the RAF's 1924 alphabet and the WWII Able Baker alphabet.
Is the code word X-ray related to medical X-rays?
It is the same word. The alphabet borrowed Röntgen's 1895 term because it was already recognized worldwide — the code word refers to the letter X, but its fame comes from medicine.
Every Letter A–Z
Previous letter: W — Whiskey · Next letter: Y — Yankee
Make It Automatic
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