This document defines key terms used in Context-Free Grammars (CFGs): terminals are symbols that cannot be replaced, non-terminals are symbols that must be replaced, and productions are the grammatical rules that specify how non-terminals can be replaced. Terminals are designated with lowercase letters, non-terminals with uppercase letters, and there is at least one production with the non-terminal S on the left-hand side.

1. CFG terminologies

2. CFG terminologies
Terminals
Non-Terminals
Productions

3. Terminals
The symbols that can’t be replaced
by anything are called terminals.

4. Non-Terminals
The symbols that must be replaced
by other things are called non-
terminals.

5. Productions
The grammatical rules are
often called productions

6. Note
The terminals are designated by small letters,
while the non-terminals are designated by
capital letters.
There is at least one production that has the
non-terminal S as its left side.