Noun gender and plurals

O dia (day) ends in -a but is masculine, and a mão (hand) is feminine, though the first -ão words you meet, o pão and o irmão, are masculine. The -ão ending is no guide on its own: a razão is feminine too, and so is every noun in -ção, such as a canção. Both are common enough that guessing will burn you, so learn them with o and a.

Nouns ending in -ão split three ways in the plural, and the word decides: coração gives corações, pão gives pães, mão gives mãos. -ões is the biggest group and the safe guess for a new word, and every noun in -ção takes it. Learn pães and mãos by heart.