"There is a map on the wall."
Translation:Hay un mapa en la pared.
brasil...... plural of el mapa = los mapas. It is masculine in all forms. Also "día" is masculine in all forms = el día, los días, But....you are correct with "águila" --- it is "el águila" but "las águilas"
All nouns in -ma are masculine. Also clima, día, mapa, poeta But this is mano, radio feminine.
brasil: Careful.......not all.........but many./////for instance, "arma" is (singular) "el arma"////(plural) "las armas", but the word is feminine
The "rule" for "el arma" (instead of using "la" is not because the "ending in -ma". :-) All nouns beginning with A use "el" for the singular, regardless of whether the noun is masculine or feminine. Otherwise, the trailing A in "la" and beginning A in "alma" would not enunciate well and would sound like a single word. Using "el" instead of "la" puts the L sound between the two A sounds.
I probably did NOT explain that very well.
I was told that there are a few words that do not stick to the masculine/feminine "rules". The best thing to do in those cases is memorize them. Like english spelling, sometimes you can't sound out the words... you just have to memorize them.