O

The letter O is the longest of the core dash-only letters in the Morse alphabet. It is slow, heavy, and very noticeable, which makes it an anchor sound in many messages and a pattern you will hear a lot once you start listening to real Morse traffic.

People often search for things like:

• What is the letter O in Morse code?
• How is the letter O represented in Morse?
• What letter is — in Morse code?
• How long is the letter O in Morse code?
• How do you know when a letter ends in Morse code?
• How do you separate letters in Morse code?

This page gives you a focused guide to the letter O: its exact pattern, timing rules, how it relates to similar letters, and simple drills to make it automatic in both decoding and sending.

Quick Answer: What Is the Letter O in Morse Code?

Here is the core fact most learners are looking for:

The letter O in Morse code is:
O = —

That means:
dash – dash – dash

In sound form, you can think of it as:

daaah – daaah – daaah

Three long signals in a row, all with the same length.

Whenever you hear three equal dashes in a row, followed by a pause, you are almost certainly listening to the letter O.

How to Write the Letter O in Morse Code

To send O correctly, you combine the simple pattern with the standard Morse timing rules.

Global timing rules:

• Dot = 1 time unit
• Dash = 3 time units
• Gap between dots and dashes inside the same letter = 1 unit
• Gap between letters = 3 units
• Gap between words = 7 units

For O = — this becomes:

1. Dash (3 units)
2. Short internal gap (1 unit)
3. Dash (3 units)
4. Short internal gap (1 unit)
5. Dash (3 units)
6. Then a 3-unit pause before the next letter

This directly answers some of the classic rule questions:

• How long is each letter in Morse code?
  Each letter is as long as its dots and dashes plus the 1-unit internal gaps. O is one of the longer common letters: three dashes plus two short internal gaps.
• How do you know when a letter ends in Morse code?
  Inside a letter, the gaps are short (1 unit). When the silence stretches to around 3 units, that marks the end of the letter and the beginning of the next one. For O, you feel dash, tiny gap, dash, tiny gap, dash, then a noticeably longer pause.
• How do you separate letters in Morse code?
  You separate letters by leaving that 3-unit gap between the end of one letter and the start of the next. That longer pause is what tells the listener “this letter is finished”.

Why O Is an Important Morse Letter

O looks simple, but it is a core building block:

• It appears in many common words: on, no, not, now, go, so, to, over, code, word, and more.
• It is one of the pure dash patterns, which trains your ear to feel long signals and not rush.
• It forms clear contrast pairs with dot-based patterns, especially the famous S vs O pairing.

In fact, O and S are perfect opposites in Morse timing:

• S = … (three dots)
• O = — (three dashes)

You can think of O as “a slow-motion S”.

O also fits into the “dash family” with T and M:

• T = –
• M = —
• O = —

If you imagine moving from T to M to O, you are just adding more dash length step by step. That makes O easier to remember as “three full dashes”.

How O Compares to Similar Morse Patterns

To keep O clear in your mind, compare it directly with nearby patterns:

• O = —
• T = –
• M = —
• S = …
• 0 (zero) = —–

Key differences:

• If you hear a single dash only, that is T.
• If you hear two dashes, that is M.
• If you hear three equal dashes and then a pause, that is O.
• If you hear three quick dots instead of three dashes, that is S, not O.
• If you hear five dashes in a row, that is the digit 0, not the letter O.

So when someone asks:

What letter is — in Morse code?
The answer is: O.

You can remember it as “three long dashes, all the same length, then stop.”

Practical Examples Using the Letter O

Seeing and hearing O inside real words helps your brain make the pattern feel natural.

Examples:

• O as a single letter: —
• ON:
  • O = —
  • N = -.
    ON = — -.
• NO:
  • N = -.
  • O = —
    NO = -. —
• GO:
  • G = –.
  • O = —
    GO = –. —
• NOT:
  • N = -.
  • O = —
  • T = –
    NOT = -. — –
• CODE:
  • C = -.-.
  • O = —
  • D = -..
  • E = .
    CODE = -.-. — -.. .

Every time you see or send these small, common words, you reinforce the idea that three dashes in a row is O.

Mini Training: Learn to Feel O ( — )

Here are a few quick drills to make the letter O feel automatic.

1. Decode the pattern

Look at or listen to:

Ask yourself:

What letter is this in Morse code?

Correct answer: O.

Repeat several times:

• Hear three long beeps, all the same length in a row → say “O” immediately.
• Visualise the letter O every time you imagine dash–dash–dash with a pause after it.

2. Encode the letter

Now reverse it.

Think of the letter O and send:

dash – dash – dash

You can tap it with your finger:

long tap, tiny gap, long tap, tiny gap, long tap.

This links the rhythm to your hand and your ear, not just your eyes.

3. Contrast O with T, M, and S

To avoid mixing O with similar letters, practise them as a small set:

• • → T
• — → M
• — → O
• … → S

Ask yourself each time:

Did I hear dots or dashes?
How many dashes were there: one, two, or three?
Were they long and even, or short and quick?

If they were three long, even dashes, you are hearing O.