A spelling alphabet (also called by various other names) is a set of words used to represent the letters of an alphabet in oral communication, especially over a two-way radio or telephone. The words chosen to represent the letters sound sufficiently different from each other to clearly differentiate them. This avoids any confusion that could easily otherwise result from the names of letters that sound similar, except for some small difference easily missed or easily degraded by the imperfect sound quality of the apparatus. For example, in the Latin alphabet, the letters B, P, and D ("bee", "pee" and "dee") sound similar and could easily be confused, but the words "bravo", "papa" and "delta" sound completely different, making confusion unlikely.

Any suitable words can be used in the moment, making this form of communication easy even for people not trained on any particular standardized spelling alphabet. For example, it is common to hear a nonce form like "A as in 'apple', D as in 'dog', P as in 'paper'" over the telephone in customer support contexts. However, to gain the advantages of standardization in contexts involving trained persons, a standard version can be convened by an organization. Many (loosely or strictly) standardized spelling alphabets exist, mostly owing to historical siloization, where each organization simply created its own. International air travel created a need for a worldwide standard.

Today the most widely known spelling alphabet is the ICAO International Radiotelephony Spelling Alphabet, also known as the NATO phonetic alphabet, which is used for Roman letters. Spelling alphabets also exist for Greek and for Russian.

Spelling alphabets are called by various names, according to context. These synonyms include spelling alphabet, word-spelling alphabet, voice procedure alphabet, radio alphabet, radiotelephony alphabet, telephone alphabet, and telephony alphabet. A spelling alphabet is also often called a phonetic alphabet, especially by amateur radio enthusiasts,^[1] recreational sailors in the US and Australia,^[2] and NATO military organizations,^[3] despite this usage of the term producing a naming collision with the usage of the same phrase in phonetics to mean a notation used for phonetic transcription or phonetic spelling, such as the International Phonetic Alphabet, which is used to indicate the sounds of human speech.

The names of the letters of the English alphabet are "a", "bee", "cee", "dee", "e", etc. These can be difficult to discriminate, particularly over a limited-bandwidth and noisy communications channel, hence the use in aviation and by armed services of unambiguous substitute names for use in electrical voice communication such as telephone and radio.

A large number of spelling alphabets have been developed over the past century, with the first ones being used to overcome problems with the early wired telephone networks, and the later ones being focused on wireless two-way radio (radiotelephony) links. Often, each communications company and each branch of each country's military developed its own spelling alphabet, with the result that one 1959 research effort documented a full 203 different spelling alphabets, comprising 1600 different words, leading the author of the report to ask:

Should an efficient American secretary, for example, know several alphabets—one for use on the telephone, another to talk to the telegraph operator, another to call the police, and still another for civil defense?^[4]

Each word in the spelling alphabet typically replaces the name of the letter with which it starts (acrophony). It is used to spell out words when speaking to someone not able to see the speaker, or when the audio channel is not clear. The lack of high frequencies on standard telephones makes it hard to distinguish an 'F' from an 'S' for example. Also, the lack of visual cues during oral communication can cause confusion. For example, lips are closed at the start of saying the letter "B" but open at the beginning of the letter "D" making these otherwise similar-sounding letters more easily discriminated when looking at the speaker. Without these visual cues, such as during announcements of airline gate numbers "B1" and "D1" at an airport, "B" may be confused with "D" by the listener. Spelling out one's name, a password or a ticker symbol over the telephone are other scenarios where a spelling alphabet is useful.

British Army signallers began using a partial spelling alphabet in the late 19th century. Recorded in the 1898 "Signalling Instruction" issued by the War Office and followed by the 1904 Signalling Regulations^[5] this system differentiated only the letters most frequently misunderstood: Ack (originally "Ak") Beer (or Bar) C D E F G H I J K L eMma N O Pip Q R eSses Toc U Vic W X Y Z. This alphabet was the origin of phrases such as "ack-ack" (A.A. for anti-aircraft), "pip-emma" for pm and Toc H for an ex-servicemen's association. It was developed on the Western Front of the First World War. The RAF developed their "telephony spelling alphabet", which was adopted by all three services and civil aviation in the UK from 1921.

It was later formally codified to provide a word for all 26 letters (see comparative tabulation of Western military alphabets).

For civilian users, in particular in the field of finance, alternative alphabets arose. Common personal names were a popular choice, and the First Name Alphabet came into common use.

Spelling alphabets are especially useful when speaking in a noisy environment when clarity and promptness of communication is essential, for example during two-way radio communication between an aircraft pilot and air traffic control, or in military operations. Whereas the names of many letters sound alike, the set of replacement words can be selected to be as distinct from each other as possible, to minimise the likelihood of ambiguity or mistaking one letter for another. For example, if a burst of static cuts off the start of an English-language utterance of the letter J, it may be mistaken for A or K. In the international radiotelephony spelling alphabet known as the ICAO (or NATO) phonetic alphabet, the sequence J–A–K would be pronounced Juliett–Alfa–Kilo. Some voice procedure standards require numbers to be spelled out digit by digit, so some spelling alphabets replace confusable digit names with more distinct alternatives; for example, the NATO alphabet has “niner” for 9 to distinguish it better from 5 (pronounced as “fife”) and the German word “nein”.

Although no radio or traditional telephone communications are involved in communicating flag signals among ships, the instructions for which flags to hoist are relayed by voice on each ship displaying flags, and whether this is done by shouting between decks, sound tubes, or sound-powered telephones, some of the same distortions that make a spelling alphabet for radiotelephony also make a spelling alphabet desirable for directing seamen in which flags to hoist. The first documented use of this were two different alphabets used by U.S. Navy circa 1908. By 1942, the U.S. Army's radiotelephony spelling alphabet was associated with the International Code of Signals (ICS) flags.^[6]

More information Symbol, c. 1908 ...

Symbol	c. 1908[7]		1920 (proposed)[8]	c. 1942[6]	1969–present[9]	ICS flag
A	Actor	Ash	Argentine	Afirm	Alpha/Alfa
B	Baker	Back	Brussels	Baker	Bravo
C	Canteen	Chain	Canada	Cast	Charlie
D	Diver	Dog	Damascus	Dog	Delta
E	Eagle	Egg	Ecuador	Easy	Echo
F	Fisher	Fox	France	Fox	Foxtrot
G	Gangway	Gig	Greece	George	Golf
H	Halliard	Horse	Hanover	Hypo	Hotel
I	Insect	Ice	Italy	Int	India
J	Jockey	Jake	Japan	Jig	Juliett
K	Knapsack	King	Khartoum	King	Kilo
L	Lugger	Lash	Lima	Love	Lima
M	Musket	Mule	Madrid	Mike	Mike
N	Neptune	Net	Nancy	Negat	November
O	Oyster	Oak	Ostend	Option	Oscar
P	Pistol	Page	Paris	Prep	Papa
Q	Quadrant	Quail	Quebec	Queen	Quebec
R	Reefer	Raft	Rome	Roger	Romeo
S	Shipmate	Scout	Sardinia	Sail	Sierra
T	Topsail	Tide	Tokio	Tare	Tango
U	Unload	Use	Uruguay	Unit	Uniform
V	Vessel	Vast	Victoria	Victor	Victor
W	Windage	Winch	Washington	William	Whiskey
X	Xray	Xray	Xaintrie	Xray	X-ray
Y	Yeoman	Yacht	Yokohama	Yoke	Yankee
Z	Zebra	Zoo	Zanzibar	Zed	Zulu

Close

While spelling alphabets today are mostly used over two-way radio voice circuits (radiotelephony), early on in telecommunications there were also telephone-specific spelling alphabets, which were developed to deal with the noisy conditions on long-distance circuits. Their development was loosely intertwined with radiotelephony spelling alphabets, but were developed by different organizations; for example, AT&T developed a spelling alphabet for its long-distance operators, another for its international operators; Western Union developed one for the public to use when dictating telegrams over the telephone;^[10] and ITU-T developed a spelling alphabet for telephone networks, while ITU-R was involved in the development of radiotelephony spelling alphabets. Even though both of these groups were part of the same ITU, and thus part of the UN, their alphabets often differed from each other. Uniquely, the 1908 Tasmanian telegraph operator's code was designed to be memorized as follows:^[11]

Englishmen Invariably Support High Authority Unless Vindictive.
The Managing Owners Never Destroy Bills.
Remarks When Loose Play Jangling. Fractious Galloping Zigzag Knights eXpeditely Capture Your Queen.

Certain languages' standard alphabets have letters, or letters with diacritics (e.g., umlauts, rings, tildes), that do not exist in the English alphabet. If these letters have two-letter ASCII substitutes, the ICAO/ITU code words for the two letters are used.

• NATO phonetic alphabet
• Allied Military Phonetic Spelling Alphabet
• APCO radiotelephony spelling alphabet
• Language-specific spelling alphabets
  • Greek spelling alphabet
  • German spelling alphabet
  • Dutch spelling alphabet
  • Russian spelling alphabet
  • Swedish Armed Forces' radio alphabet
  • Japanese radiotelephony alphabet
  • Korean spelling alphabet
• Cockney alphabet