Combination

A forcing variation that uses tactical elements to exploit special conditions in the position and achieve a particular goal. A sacrifice is a characteristic, usually accompanying, feature of a combination.

Conditions and purpose

The special conditions may consist of: the enemy king's exposure to mate or perpetual check; undefended pieces, or the chance for a weaker piece to attack a stronger one; a far-advanced passed pawn; or almost all of one's own pieces having no moves (stalemate combinations).

These special conditions let the side carrying out the combination choose a line that uses at least two tactical elements (double attack, pin, and so on). This line is forcing, since every move either creates a threat or meets one.

The goal of a combination can be to deliver mate or stalemate, to gain a material or positional advantage, to repel the opponent's attack, to ease one's defense, and so on.

A sacrifice — voluntarily handing the opponent a material advantage — is almost always part of a combination.

Aesthetics

A combination embodies the most essential elements of chess's beauty. Its aesthetic effect rests on originality (surprise), purposefulness, logic (arising from the whole course of the struggle), and complexity (length, numerous branches). A combination is more beautiful when forcing moves alternate with quiet ones that create no overt threats.