∞

The ∞ symbol means that the position is unclear or uncertain. The annotator cannot reliably summarize it as equal, better for White, or better for Black because the position contains complications, compensation, or plans that are hard to compare.

An unclear position need not be objectively balanced. Deeper analysis may eventually favor one side, but at the annotated point there are enough practical or tactical possibilities to resist a simple verdict. That is why = and ∞ are not interchangeable.

The sign often appears with attacks against both kings, sacrifices whose compensation is uncertain, or many forcing variations. It does not mean that the game lasts forever, that an engine calculated indefinitely, or that the result will be a draw.

In PGN, the unclear-position category is NAG $13. Some text systems use ~ or the word inf as substitutes, but the chess meaning remains uncertainty in the assessment.