  In this paper, we present the universal structure of the alphabet of one-loop
Feynman integrals. The letters in the alphabet are calculated using the Baikov
representation with cuts. We consider both convergent and divergent cut
integrals and observe that letters in the divergent cases can be easily
obtained from convergent cases by applying certain limits. The letters are
written as simple expressions in terms of various Gram determinants. The
knowledge of the alphabet enables us to easily construct the canonical
differential equations of the $ d\log $ form and aids in bootstrapping the
symbols of the solutions.
