Military Alphabet · Letter S
S in the Military Alphabet: Sierra
Code word, pronunciation, history, and how to use it when spelling out loud
In the military alphabet, the letter S is Sierra, pronounced see-AIR-rah. It is the NATO/ICAO phonetic alphabet's code word for S, standard on military, aviation, and marine radio since March 1956, when it took over from the wartime word Sugar.
Why "Sierra"?
Sierra is the Spanish word for a saw, from the Latin serra, and Spanish has long applied it to jagged mountain ranges — the Sierra Nevada in Spain and the one in California both carry the name. ICAO's postwar selection work demanded words alive in English, French, and Spanish alike, and Sierra is one of the alphabet's most clearly Spanish contributions. Its three open syllables also transmit well through static. Like most of the alphabet, it entered with the 1951 version and held its place through the 1956 revision.
S Across Spelling Alphabets
| Alphabet | Word for S |
|---|---|
| NATO/ICAO | Sierra |
| LAPD | Sam |
| Western Union | Sugar |
| German (Classic) | Samuel |
| German (DIN 5009:2022) | Salzwedel |
| French | Suzanne |
| Spanish | Sábado |
| Italian | Savona |
| Able Baker (WWII, historical) | Sugar |
| RAF 1924 (historical) | Sugar |
British WWI signalese rendered S as "Esses"; from 1924 the RAF used Sugar, and the 1943 Able Baker alphabet kept it — which is why Bomber Command aircraft were logged with names like "S for Sugar." Sierra replaced Sugar across NATO in 1956.
Sierra in the Field
US Navy submarine crews designate sonar contacts with this letter — a new contact becomes "Sierra One," the next "Sierra Two" — since sonar is how a submerged boat hears the world. Fighter pilots have their own use: "Sierra Hotel" is old squadron slang spelling out a two-word compliment, politely translated as "extremely good." More routinely, Sierra appears in taxiway instructions and aircraft call signs, spoken wherever the bare letter S could blur into F or X-sounds on a poor channel.
"S as in Sierra" on the Phone
It's Sylvie with an S — S as in Sierra, Y, L, V, I, E.
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
NATO used its own alphabet against the other side: Sierra was the NATO reporting name for a class of Soviet titanium-hulled nuclear attack submarines built in the 1980s.
Frequently Asked Questions
What is S in the military alphabet?
S is Sierra in the NATO phonetic alphabet, pronounced see-AIR-rah. It has been the standard radio code word for S in military and aviation use since 1956.
How do you pronounce Sierra?
The ICAO respelling is see-AIR-rah, with the stress on the middle syllable. All three syllables are voiced — see, air, rah.
What was S before Sierra?
S was Sugar in both the RAF's 1924 alphabet and the WWII Able Baker alphabet, and "Esses" in British WWI signalese before that. Sierra replaced Sugar when the ICAO alphabet took effect in March 1956.
What does Sierra Hotel mean?
It is fighter-pilot slang built from the phonetic letters S and H, spelling the initials of a blunt two-word phrase of high praise. Calling a pilot or a maneuver "Sierra Hotel" means it was outstanding.
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