http://spanish.about.com/od/nouns/a/nouns.htm?nl=1 Here are 10 facts about Spanish nouns that will come in handy as you learn Spanish: 1. Spanish nouns have gender , and nearly all are either masculine or feminine . Although male creatures are usually (not always) represented by masculine nouns and female creatures by feminine nouns, in most cases the gender of a noun appears arbitrary. 2. The only neuter (neither masculine nor feminine) nouns are abstract nouns , which are formed by preceding a descriptive adjective with the definite article lo . For example, you could say lo importante to form a neuter noun (or an adjective functioning as a noun) meaning "the important thing." 3. Adjectives referring to nouns must agree with the noun in number and gender. For example, in the sentence " Las casas son nuevas " ("The houses are new"), casas is plural and feminine, and so are las and nuevas . 4. Nouns that end in o are usually masculine, and