In natural language sentence grammar, this will be the symbol corresponding to a sentence. In computer languages, it might be the symbol corresponding to a complete program. In parsing, the start symbol is either the start state of a derivation or the goal state. More concretely in context-free grammars, a production states one way in which a phrase of a given type may be constructed from specific types of constituents. In a production rule, or a state of a derivation, a symbol from the basic vocabulary of the language.
Terminals can only occur on the right-hand side of productions.
A symbol used in a grammar, in production rules, but which does not occur as a terminal. These include the symbols for the parts of speech and for phrase types. Bottom up An attempt to find a derivation of a phrase which starts from the phrase itself and which if successful leads to the start symbol or another phrasal symbol. Derivation A sequence of states which constitutes a proof that a certain string can be analysed as a phrase of a certain category. Each state is licenced by the application of a production to its predecessor state.