(m) significa que un sustantivo es de género masculino (p. ej. el hombre, el sol).
(M)
It's advisable to have some savings as a kind of insurance policy in case you lose your job.Es recomendable tener ahorros que sirvan de colchón en caso de que pierdas el trabajo.
b.
Una frase idiomatica cuyo significado no es deducible si se traduce palabra por palabra.
Having that photo in his possession is a kind of insurance policy. Sophie won't say anything against him so long as he has it.Tener esa foto en su poder es su as en la manga. Sophie no dirá nada contra él mientras la tenga.
She's applied to other universities as an insurance policy in case she doesn't get into Oxford.Para asegurarse plaza, ha enviado solicitudes a otras universidades por si no consigue entrar en Oxford.