malus

Malus, mala, malum declines like bonus, and like bonus its comparison is suppletive: peior, "worse", and pessimus, "worst", come from a different root entirely. English does the same thing with bad, worse, worst, so the oddity feels familiar. The neuter malum is a noun in its own right, "an evil, a misfortune", and mala in the plural is "troubles".

The trap is malum, "apple", which is spelled identically but has a long a in the first syllable and comes from Greek melon. The medieval pun that made the forbidden fruit an apple depends on that collision and is not classical. A second trap: mala is also the noun "cheek, jaw", so a bare mala needs context. Family: malitia, malignus, maledico, malefactor. Spanish malo, French mauvais displaced it partly, and English took malice, malign, malady, malaria and dismal.