Like English, Spanish uses several prefixes that are derived from the Latin prefix de-, which originally conveyed the idea of separation and came to be used in ways that often indicated a distinct change in meaning, even an opposite one, from the original word. The prefixes take similar forms in the two languages: In Spanish, des- is perhaps the most common, as in desempleo, while de-, as in decolorar, and dis-, as in disconformidad, are also used. English tends to use "de-," as in "deconstruct," and "dis-," as in "disability," the most frequently.
Although you can seldom predict which prefix might be used with a particular word, you can often use your knowledge of the prefixes' meanings to figure out what unfamiliar words mean. Here are the most common ways in which des- and the related prefixes are used in Spanish:
To indicate negation of a verb or reversal of its action: In this way, the Spanish des- can be the equivalent not only of "de-," but also of "un-." For example, hacer is an everyday verb used to mean "to do" or "to make," while deshacer can usually be translated as "to undo" or "to unmake."
- Ayer llegó el equinoccio de otoño, y el Ártico no se desheló por completo. Yesterday the fall equinox arrived, and the Arctic had not thawed completely. (Helar means "to freeze," so deshelar is used to refer to thawing.)
- El cantante canadiense se deshidrató mientras estaba en el escenario. The Canadian singer got dehydrated while on the stage. (Hidratar means "to hydrate" or "to moisturize," so deshidratar means "to dry out" or "to dehydrate.")
- Es importante que desinfles el neumático por completo antes de empezar a trabajar en el mismo. It is important that you deflate the tire completely before beginning to work on it. (Inflar usually means "to inflate.")
- Te recomiendo que utilice agua oxigenada para decolorar el pelo. I recommend that you use hydrogen peroxide in order to bleach your hair. (The verb here for "to bleach" literally means "to take the color from.")
Similarly, to indicate the lack of something:
- La actitud del gobierno ante irregularidades genera desconfianza. The government's attitude in face of irregularities creates distrust. (Confianza refers to trust or confidence.)
- Desempleo or desocupación hace referencia a la situación del trabajador que carece de trabajo. Unemployment or joblessness refer to the situation of a worker who lacks work.
- La mayor fuente de disconformidad laboral es la falta de reconocimiento. The major source of labor conflict is the lack of recognition. (Conformidad frequently refers to agreement, making it a false friend.)
- Un doctor no puede curar un corazón roto por desamor. A doctor cannot cure a heart broken by lack of love.
Occasionally, to make the meaning of a word stronger: This occurs most often with root words that indicate a lack or diminution of something.
- Lava tu ropa al revés, y la ropa no se desgastará tan rápidamente. Wash your clothing inside-out, and it won't wear out so quickly. (The conjugated form of gastar could have been used here, but desgastar is stronger.)
Occasionally, to give a word a negative meaning: Although not common, in this way des- can function something like mal-.
- Es villano irredimible, irreverente y deslenguado. He is a irredeemable, irreverent and foul-mouthed villain. (Lengua is the word for tongue.)
A note about dis-: The prefix dis- is sometimes used as the equivalent of the English prefix "dys-," referring to an anomaly or difficulty, as in dislexia (dyslexia) and disfuncional (dysfunctional). This prefix, although more obviously so in English than in Spanish, isn't related to the uses of the prefixes discussed above. It comes not from Latin, but from the Greek prefix dys-.