#### 9.2.4 Implicit Entity Definition

It is not required to explicitly define an entity before it is used. Just typing the arrow definition `a->b;` will automatically define entities ‘`a`’ and ‘`b`’ if not yet defined. This behaviour can be disabled by specifying the `--pedantic` command-line option or specifying `pedantic=yes` chart option. See Chart Options. Disabling implicit definition is useful to generate warnings for mis-typed entity names39.

Implicitly defined entities always appear at the very top of the chart. If you want an entity to appear only later, define it explicitly.

#### Footnotes

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To this end, color syntax highlighting underlines an entity name appearing the first time. This allows quickly realizing if the name of an entity is misspelled.