FIRST Set in Syntax Analysis - GeeksforGeeks
FIRST(X) for a grammar symbol X is the set of terminals that begin the strings derivable from X. Rules to compute FIRST set: If x is a terminal, then FIRST(x) = { 'x' } If x-> Є, is a production rule, then add Є to FIRST(x).
https://www.geeksforgeeks.org/first-set-in-syntax-analysis/