(m) significa que un sustantivo es de género masculino (p. ej. el hombre, el sol).
(M)
His entrance into the university was guaranteed because his father was an important donor.Su ingreso a la universidad estaba garantizado porque su padre era un donante importante.
(f) significa que un sustantivo es de género femenino (p. ej. la mujer, la luna).
(F)
She was denied entrance to the school because she had failed too many classes.Le negaron la entrada en el colegio porque había suspendido demasiadas asignaturas.
The artists entranced the crowd for two hours straight with their incredible performances.Los artistas extasiaron al público durante dos horas sin parar con sus actuaciones impresionantes.