determinant

noun

• 1a factor that decisively affects the nature or outcome of something:pure force of will was the main determinant of his success
• Biology a gene or other factor that determines the character and development of a cell or group of cells in an organism, a set of which forms an individual’s idiotype.

• 2 Mathematics a quantity obtained by the addition of products of the elements of a square matrix according to a given rule.

adjective

• serving to determine or decide something.