“…The principal advantage of spectral methods lies in their capacity to accomplish with high accurate outcomes. There are four popular methods of spectral methods; they are tau, collocation, Galerkin, and spectral element methods, see the studies of Rainville, Ezz-Eldien and Doha, Dehghan and Abbaszadeh, Dehghan, Abbaszadeh, and Mohebbi, Bernardi and Maday, and Canuto et al [37][38][39][40][41][42][43] The choice of the appropriate utilized spectral method suggested for solving such differential equations depends certainly on the type of the differential equation and also on the type of the initial or boundary conditions governed it, see the studies of Hafez et al, Abd-Elhameed and Youssri, Vanani and Aminataei, and Saker, Bhrawy, and Ezz-Eldien. [44][45][46][47] In recent decades, tau and collocation spectral approaches have been utilized for the solution of various types of FDEs, see the studies of Li et al, Khosravian-Arab, Dehghan, and Eslahchi, Saadatmandi and Dehghan, Ezz-Eldien, Dehghan, Manafian, and Saadatmandi, Kashkari and Syam, and Zaky et al [48][49][50][51][52][53][54] The essential purpose of the present article is to build a novel spectral algorithm based on the shifted Jacobi modified Galerkin method (SJMGM) for solving FDEs and system of FDEs (SFDEs) governed by homogeneous and nonhomogeneous initial and boundary conditions.…”