Main Page | See live article | Alphabetical index In mathematics, the digamma function is defined by where D is the differential operator. The digamma function, often notated also ψ0(x) or even ψ0(x), is related to the harmonic numbers in that where Hn-1 is the (n-1)'th harmonic number, and γ is the well-known Euler-Mascheroni constant. Also see Gamma function Polygamma function Harmonic number This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License.