Demonstrative adjectives

http://spanish.about.com/od/adjectives/a/demonstrative_adjectives.htm

Demonstrative adjectives are those adjectives whose function is to point at something. In English, the singular demonstrative adjectives are "this" and "that," while the plural ones are "these" and "those." (Some grammarians refer to them as demonstrative determiners.)
Unlike English, Spanish has three sets of demonstrative adjectives, which vary by number and gender, so there are 12 in all, as shown in the list below. Translations are included in parentheses.

• singular masculine
  • este (this)
  • ese (that)
  • aquel (that)
• plural masculine
  • estos (these)
  • esos (those)
  • aquellos (those)
• singular feminine
  • esta (this)
  • esa (that)
  • aquella (that)
• plural feminine
  • estas (these)
  • esas (those)
  • aquellas (those)

Note that the masculine singular forms don't end in -o. The demonstrative adjectives typically are placed before the nouns they modify. They must match the noun in both number and gender. A few examples:

• Me gusta este perro. I like this dog.
• Prefiero estas computadoras. I prefer these computers.
• Voy a comprar ese coche. I'm going to buy that car.
• Me gustan aquellas casas. I like those houses.

Although both ese and aquel and their related forms can be translated as "that" or "those," there are some distinctions in meaning. Ese and its related forms are more common, and you're generally safe to use them when in English you'd use "that" or "those." However, aquel and its related forms refer to something that's farther away in terms of distance or time. Although ese and its forms can be used for an object near the speaker or listener, aquel cannot. The distinction can be translated in a number of different ways, as the examples indicate:

• Me gustan esos perros. I like those dogs.
• Me gustan aquellos perros. I like those dogs over there.
• No quiero esa casa. Quiero aquella casa. I don't want that house. I want that house farther back.
• ¿Recuerdas esos días? Do you remember those days?
• ¿Recuerdas aquellos días? Do you remember those days long ago?

Items in a series: When two or more items are in a series, the demonstrative adjective must be used with each item. While in English we would say "those cats and dogs," in Spanish we would say esos perros y esos gatos. Use of just one demonstrative adjective in this case, as in esos perros y gatos, would imply that we're talking about animals that are a cross between a cat and a dog.