In the Morse code, which letter is indicated by 3 dots?

The story behind the answer

In International Morse code, the letter S is three short signals (dots): ... This fits the system where common letters get shorter patterns—E is a single dot, T a single dash, and S, also common, is three quick dits. By contrast, A is .-, O is --- (three dashes), and C is -.-., so only S matches three dots.

Morse code, developed in the 1830s–1840s by Samuel Morse and Alfred Vail, was designed for efficient telegraph and later radio communication. A great memory hook is the famous distress call SOS: ... --- ... The opening and closing “...” are the S’s, and the long “---” in the middle is O, reinforcing that S is three dots and O is three dashes.