Translators always risk inappropriate spill-over of source-language idiom and usage into the target-language translation. On the other hand, spill-overs have imported useful source-language calques and loanwords that have enriched the target languages. Indeed, translators have helped substantially to shape the languages into which they have translated.

Due to the demands of business documentation consequent to the Industrial Revolution that began in the mid-18th century, some translation specialties have become formalized, with dedicated schools and professional associations.

Because of the laboriousness of translation, since the 1940s engineers have sought to automate translation (machine translation) or to mechanically aid the human translator (computer-assisted translation). The rise of the Internet has fostered a world-wide market for translation services and has facilitated language localization.

The word translation derives from the Latin translatio (which itself comes from trans- and fero, together meaning "to carry across" or "to bring across"). The modern Romance languages use words for translation derived from that source and from the alternative Latin traduco ("to lead across"). The Germanic and Slavic languages likewise use calques based on these Latin sources.

The Ancient Greek term for translation, μετάφρασις (metaphrasis, "a speaking across"), has supplied English with metaphrase (a "literal translation", a "word-for-word" translation) and paraphrase ("a saying in other words", from παράφρασις, paraphrasis). In contemporary usage, metaphrase corresponds to "formal equivalence", and paraphrase corresponds to "dynamic equivalence."

A secular icon for the art of translation is the Rosetta Stone. This trilingual (hieroglyphic-Egyptian, demotic-Egyptian, Ancient-Greek) stele proved to be the translator’s key to decryption of Egyptian hieroglyphs for Thomas Young, Jean-François Champollion and others.

Discussions of the theory and practice of translation reach back into antiquity and show remarkable continuities. The ancient Greeks distinguished between metaphrase (literal translation) and paraphrase. This distinction was adopted by English poet and translator John Dryden (1631–1700), who described translation as the judicious blending of these two modes of phrasing when selecting, in the target language, "counterparts," or equivalents, for the expressions used in the source language:

Dryden cautioned, however, against the license of "imitation", i.e., of adapted translation: “When a painter copies from the life... he has no privilege to alter features and lineaments..."

This general formulation of the central concept of translation — equivalence — is as adequate as any that has been proposed since Cicero and Horace, who, in first-century-BCE Rome, famously and literally cautioned against translating "word for word" (verbum pro verbo).

Despite occasional theoretical diversity, the actual practice of translation has hardly changed since antiquity. Except for some extreme metaphrasers in the early Christian period and the Middle Ages, and adapters in various periods (especially pre-Classical Rome, and the 18th century), translators have generally shown prudent flexibility in seeking equivalents — "literal" where possible, paraphrastic where necessary — for the original meaning and other crucial "values" (e.g., style, verse form, concordance with musical accompaniment or, in films, with speech articulatory movements) as determined from context.