You might use a language other than English for the same reasons you might use different varieties of English: to represent the actual words of a speaker, to make a point, to connect with your audience, or to get their attention.
See how Gerald Haslam uses Spanish to capture his great-
“Expectoran su sangre!” exclaimed Great-
“De los ojos,” Grandma added. “From their eyes,” mother explained, herself uncomfortable in the presence of the small beast.
I grinned, “Awwwwwww.”
But my Great-
“His name’s John,” I said.
—GERALD HASLAM, California Childhood
In the following passage, notice how the novelist Michele Herman uses Yiddish to evoke her grandmother’s world:
“Skip shabes?” Rivke chuckled. “I don’t think this is possible. Once a week comes shabes. About this a person doesn’t have a choice.”
“What I mean”—Myra’s impatience was plain—
“Ach,” Rivke said. “Too much for me it isn’t.” This wasn’t true. For some time she had felt that it really was too much for her. It was only for shabes that she cooked; the rest of the week she ate cold cereal, fruit, pot cheese, crackers.
—MICHELE HERMAN, Missing
In this passage, Rivke’s syntax—
In the following passage, a linguist uses Spanish, with English translations, in her discussion of literacy in a Mexican community in Chicago:
Gracia (grace, wit) is used to refer to wittiness in talk; people who tiene gracia (have grace, are witty) are seen as clever and funny. Not everyone illustrates this quality, but those who do are obvious from the moment they speak. As one middle-
. . . cuando ellos empiezan a hablar, desde el momento que los oyes hablar, tienen gracia. Entonces, la gente que tiene gracia, se va juntando gente a oírlos. Y hay gente más desabrida, diría yo. No tiene, no le quedan sus chistes. Aunque cuente uno una charrita . . . ya no te vas a reír igual.
(. . . when they start to speak, from the moment that you hear them speak, they are witty. So then, the people who are witty begin to have a listening crowd gather about them. And then there are people who are more boring, I would say. They don’t have, their jokes just don’t make it. Even though they may tell a joke...you’re not going to laugh in the same manner.)
—MARCIA FARR, “Essayist Literacy and Other Verbal Performances”
Here, Farr provides a translation of the Spanish, for she expects that many of her readers will not know Spanish. She evokes the language of the community she describes, however, by presenting the Spanish first.
In general, you should not assume that all your readers will understand another language. So, in most cases, including a translation (as Marcia Farr does) is appropriate. Occasionally, however, the words from the other language will be clear from the context (as is shabes in Michele Herman’s passage). At other times, a writer might leave something untranslated to make a point—
Considering Disabilities: American sign language