#### 12.1.1 Control sequence, control word and control symbol

When reading input TeX converts the sequences of read characters into a sequence of tokens. When TeX sees a backslash `\`, it will handle the following characters in a special way in order to make a control sequence token.

The control sequences fall into two categories:

• control word, when the control sequence is gathered from a `\` followed by at least one ASCII letter, followed by at least one blank. The sequence of at least one ASCII letter is called the control sequence name.
• control symbol, when the control sequence is gathered from a `\` followed by one non-letter character.


Just as the `\relax` command does nothing, the following will print ‘Hello!’:

```Hel\relax
lo!
```

This is because blanks after `\relax`, including the newline are ignored, and blanks at the beginning of a line are also ignored (see Leading blanks).