The authors offer a (generalized) Hyers-Ulam [\textit{S. M. Ulam}, Problems in modern mathematics, Wiley, New York (1964; Zbl 0137.24201), Ulam originally posed the problem in 1940; \textit{D. H. Hyers}, Proc. Nat. Acad. Sci. USA. 27, 222--224 (1941; Zbl 0061.26403)] stability result for the functional equation \[ \begin{multlined} f(x_1+x_2+2x_3)+f(x_1+x_2-2x_3)+f(2x_1)+f(2x_2)+7[f(x_1)+f(-x_1))]\\ =2f(x_1+x_2) +4[f(x_1+x_3)+f(x_1-x_3)+f(x_2+x_3)+f(x_2-x_3)]\end{multlined} \] where \(x_j\) is orthogonal to \(x_k\;(j,k=1,2,3, j\neq k)\) in the sense of \textit{J. Rätz} [Aequationes Math. 28, 35--49 (1985; Zbl 0569.39006)] in real vector spaces and for its generalization to \(n\geq 3\) variables. Structure and language is somewhat unorthodox but the meaning gets through. The paper starts with a survey on Hyers-Ulam stability. Among the 32 references only one is from between Hyers's 1941 paper and a 1978 paper by \textit{Th. M. Rassias} [Proc. Am. Math. Soc. 72, 297--300 (1978; Zbl 0398.47040)], for the result and proof cf., however, \textit{T. Aoki} [J. Math. Soc. Japan 2, 64--66 (1950; Zbl 0040.35501), not in the references]. For example also a paper by \textit{D. G. Bourgin} [Bull. Am. Math. Soc. 57, 223--237 (1951; Zbl 0043.32902)] and another paper by \textit{D. H. Hyers} [Pac. J. Math. 11, 591--602 (1961; Zbl 0099.10501)] could have been quoted. For the core of the direct method for proving Hyers-Ulam stability, see \textit{G.-L. Forti} [J. Math. Anal. Appl. 295, No. 1, 127--133 (2004; Zbl 1052.39031)].