Fill in the Blanks UN/UNA ReviewOnline version When should I use 'un' and when should I use 'una'? Use "un" with masculine words and "una" with feminine words. But, how do I know when a word is masculine or feminine? Most words that end with ‘a’ are feminine. The rest could be masculine but there are exceptions. Write un or una, according to the gender of the word. by Ms. Gutiérrez 1 When should I use 'un' and when should I use 'una' ? Use " un " with masculine words and " una " with feminine words . But , how do I know when a word is masculine or feminine ? Most words that end with ? a' are feminine . Example : mesa and silla are feminine . Libro and borrador are masculine . Remember that the meaning of UN - UNA is 'a' / 'an' . Example : A book = Un libro , A bookback = Una mochila Write un or una , according to the gender of the word . 1 . sandía 2 . pera 3 . fresa 4 . coco 5 . kiwi 6 . naranja 7 . uva 8 . limón 9 . mango 10 . piñ a