Today's word is the adjective MALUS, meaning "bad," with the adverbial form, "badly," male. This word is notorious for causing confusion because there is also a second declension masculine noun mālus (note the long "a" in the stem), meaning "a beam" or the "mast" of a ship. There is also a feminine second declension noun, mālus, meaning "apple tree" (and likewise mālum, "apple"). If that were not already bad enough, there is also māla, a feminine first-declension noun meaning "cheek-(bone), jaw." In context, of course, these words are not likely to cause confusion, but you do have to be prepared to anticipate these possible different readings, especially if you are reading a text that is not marked with macrons.
We get a tremendous number of English words from the Latin root in malus, including those words with mal- as a prefix: "malevolent," "malformed," "malodorous," and on and on. Via the Italian, we get "malaria," from the (mistaken) belief that it was a bad property of the air itself which caused the disease. From Latin dies mali, the says of wickedness or bad luck, we get "dismal." From Latin male habitus, via French malade, we get "malady."
Here are some examples of today's word in Latin sayings and proverbs; for more information, see the page at the Scala Sapientiae, which contains notes on some of the proverbs cited below, as well as additional proverbs:
Qui sibi malus, cui bonus?
Qui sibi malus, nulli bonus.
Bonus esse non potest aliis malus sibi.
Audies male, si male dicas.
Mors nec bonum nec malum est.
Malum quidem nullum sine aliquo bono.
Quaerite bonum et non malum.
Nulli malum pro malo.
Bonum ex malo non fit.
Malum bono vince.
Male creditis hosti.
Male vivunt qui se semper victuros putant.
Saepe malum petitur; saepe bonum fugitur.
Lex mala, lex nulla.
Ex malis moribus fiunt bonae leges.
Qui numquam male, numquam bene.
Malum bene positum ne moveas.
Nulli malum pro malo reddete.
Alia ex aliis mala oriuntur.