A tight-binding approach comprising a pz orbital basis set is employed to induce a bandgap in massless Dirac Fermion, graphene. The role of the structural parameter, chirality, has been explored to determine the electronic band structure of armchair graphene nanoribbon (AGNR). The present results show that the key parameter, the bandgap in quasi-one-dimensional graphene nanoribbon, arises from quantum confinement. It is observed that the total number of carbon atoms present in the overall unit cell of AGNR is equal to the total number of subbands in the corresponding electronic structure. Important band structure parameter effective mass is computed from the parabolic region of the band structure. A decreasing trend of energy bandgap and effective mass as a function of width has been reported. Our results demonstrated that armchair graphene nanoribbon can be divided into three families 3p, 3p+1, and 3p+2, p is an integer. In addition, the electronic density of states at different chirality values has been studied, to support our findings of the electronic band structure.
