Add statement section description

doc/language.tex

@@ -335,5 +335,21 @@ relations $=$ and $<>$ apply to all types.
 
 \chapter{Statements}
 
+\begin{grammar}
+<statement> = <assignment> | <procedure-call> | <defer-statement>
+    | <label-declaration> | <goto-statement> |
+    | <while-statement> | <if-statement> | <case-statement>.
+\end{grammar}
+
+Statements denote actions. There are elementary and structured statements.
+Elementary statements are not composed of any parts that are themselves
+statements. They are the assignment and the procedure call. Structured
+statements are composed of parts that are themselves statements. They
+are used to express sequencing and conditional, selective, and
+repetitive execution. A statement may also be empty, in which case it
+denotes no action. The empty statement is included in order to relax
+punctuation rules in statement sequences.
+
+\section{Elementary statements}
 \section{Conditional statements}
 \section{Loop statements}