A context-free grammar satisfies the LL(1) condition if it satisfies the following three conditions:

• All of its productions have pairwise disjoint first sets
• If a concatenation of nonterminals $𝐴\otimes 𝐵$ appears in a production, then $𝐴$ has a disjoint followlast set from the first set of $𝐵$
• At most one production is nullable

This is essentially the type system of [1], which characterizes the LL(1) condition for context-free expressions.

Intutively, an LL(1) grammar can be parsed unambiguously, and without backtracking, by a predictive parser that only needs one token of lookahead.