In mathematics, positive definiteness is a property of any object to which a bilinear form or a sesquilinear form may be naturally associated, which is positive-definite. See, in particular:
Positive-definite bilinear form Positive-definite function Positive-definite function on a group Positive-definite functional Positive-definite kernel Positive-definite matrix Positive-definite operator Positive-definite quadratic form
References Fasshauer, Gregory E. (2011), "Positive definite kernels: Past, present and future" (PDF), Dolomites Research Notes on Approximation, 4: 21–63. Stewart, James (1976), "Positive definite functions and generalizations, an historical survey", The Rocky Mountain Journal of Mathematics, 6 (3): 409–434, doi:10.1216/RMJ-1976-6-3-409, MR 0430674.