#### 3.1.1 Identifiers

Identifiers in `sketch` are references to earlier-defined options, scalars, points, vectors, transforms, drawables, and tags. Definitions are explained in Definitions.

An identifier consists of a leading letter followed by letters, numbers and underscores. The last character may not be an underscore. Keywords cannot be used as identifiers, and reserved words ought to be avoided. See Key and reserved words.