A tree defining the syntactic structure of a sentence in a context-free language. The interior nodes are labeled by nonterminals of the context-free grammar; the descendants of a node labeled by A, say, spell from left to right the right-hand side of some production having left-hand side A. The leaf nodes of a parse tree may be terminals or nonterminals. If all the leaves are terminals then they spell from left to right a sentence of the language.An example of a parse tree is shown in the diagram. It is assumed that the grammar in question has productions A → BC, B → b, C → cc Note that it is conventional for the top of the tree to be its root and the bottom to be its leaves.
A → BC, B → b, C → cc
An early stage in compiling a program usually consists of generating a parse tree in which the constructs that make up the program are expressed in terms of the syntax of the programming language.