Why S matters
S is three quick dots — the opening and closing of the SOS distress signal. If you only learn one morse letter in your life, make it S. It's recognisable anywhere, in any medium, to anyone trained in wireless.
Memorization tip
Three dots — the 'S' in SOS. The most famous letter in morse.
Common English words starting with S
Where this letter appears in the ITU alphabet
The full A–Z chart shows every letter side-by-side so you can see the pattern of dots and dashes. For just the numbers, see morse code numbers 0–9. For a printable version, the chart page combines letters, digits, and punctuation in one layout.
The history of S
S comes from the Phoenician shin, meaning tooth, drawn as a row of pointed teeth. The Greeks adopted it as sigma, with several regional shape variants; the Romans settled on the curved form we still use today. In English, S is the tenth most common letter — modest in raw frequency but enormously important because it forms the plural ending of nearly every English noun and the third-person-singular ending of nearly every English verb.
S in CW operating
S is the opening and closing third of SOS — three dots, the most recognized morse pattern in human history. SOS was adopted as the international maritime distress signal at the 1906 Berlin International Wireless Telegraph Convention, replacing the earlier CQD signal. S is also part of SK — the prosign for 'end of contact' or, in funeral contexts, the final transmission for a silent key (a deceased operator). Sending SK closes a QSO definitively.
What position 10 means in practice
S at position 10 with 6.3% frequency means about one S every sixteen characters of running English — high frequency driven almost entirely by the plural noun ending and the third-person-singular verb ending, both of which add an S to a huge fraction of English content words. In CW, S is the opening and closing of SOS, the most-recognized pattern in the international code, and is part of the SK end-of-contact prosign. The three-dot pattern is the middle of the all-dots family, sandwiched between I (two) and H (four), and miscount errors at speed are some of the most common copying mistakes a Koch learner makes.
How to drill it
S is three dots, the middle of the all-dots family between I (two dots) and H (four dots). The two failure modes are miscounting (hearing two dots as I or four as H) and gap-misreading (hearing two consecutive I's as a single H). Drill S with I and H in random rotation at 18+ WPM and the rhythm becomes automatic within a few sessions.
Most-confused with: H, I, 5 — drill them together.
Sample copy: “She sees several silver swans swim slowly.”
Frequently asked questions
What is the letter S in morse code?
The letter S in international morse code is "..." — 3 symbols.
How do I remember the morse code for S?
Three dots — the 'S' in SOS. The most famous letter in morse.
How common is the letter S in English?
S is position 10 in English frequency, appearing in about 6.3% of running text.