With-the-idea annotation symbol

△ is read as with the idea of. It connects a move to the later plan, threat, or continuation that explains why the move was chosen. An annotation may show a quiet move, add △, and then give the pawn advance or piece route the player intends.

The sign explains purpose, not quality. It does not claim that the move is good, that the idea will work, or that the following sequence is forced. The opponent may choose another reply, prevent the plan, or accept a different consequence.

In NAG lists, where NAG means Numeric Annotation Glyph, it appears as a Chess Informant proposal for preserving this relationship in a digital game. Its main value is to separate the move that was played from the strategic or tactical reason the annotator wants to show.