Question: is poema masculine or feminine?
Answer: Most nouns that end in 'o' are masculine, and most that end in 'a' are feminine - but this is not the rule for every word! There are some words which end in 'a' that are masculine (el mapa, el problema, el día, el planeta, el poema...) And a few words that end in 'o' are feminine (la radio, la mano...)