When important terms are first defined, they are formatted like this. Most sections begin with an example of a syntactic construct followed by corresponding grammar rules. The grammar rules are expressed in a variant of Backus-Naur form. Nonterminal symbols begin with a letter and are represented by strings of letters and underscores in an italic font. The nonterminal symbol on the lefthand side of a grammar rule is followed by a double arrow ==> and the right-hand side of the rule. The terminal symbols consist of Sather keywords and special symbols and are typeset like this. Vertical bars ...|... separate alternatives, parentheses (...) are used for grouping, square brackets [...] enclose optional clauses and braces {...} enclose clauses which may be repeated zero or more times. Multi-line examples are indented after the first line, and an ellipsis '...' indicates code that has been left out for clarity. Semicolons are used to separate examples only if, when taken together, the examples could be a legitimate section of Sather code. Trailing semicolons, which are optional, are not shown.