Language interpreting or interpretation is the intellectual activity of facilitating oral and sign-language communication, either simultaneously or consecutively, between two or more users of different languages. Functionally, interpreting and interpretation are the descriptive words for the activity. In professional practice interpreting denotes the act of facilitating communication from one language form into its equivalent, or approximate equivalent, in another language form. Interpretation denotes the actual product of this work, that is, the message as thus rendered into speech, sign language, writing, non-manual signals, or other language form. This important distinction is observed to avoid confusion.

Functionally, an interpreter is a person who converts a source language to a target language. The interpreter's function is conveying every semantic element (tone and register) and every intention and feeling of the message that the source-language speaker is directing to the target-language listeners.

Interpreting versus translation

Despite being used interchangeably, interpretation and translation are not synonymous, but refer, respectively, to the spoken and written transference of meaning between two languages. Interpreting occurs in real time, in the presence — physical, televised, or telephonic — of the parties for whom the interpreter renders an interpretation. Translation is the transference of meaning from text to text (written, recorded, sign), with the translator having time and access to resources (dictionaries, glossaries, etc.) to produce a faithful, true, and accurate document or verbal artifact.

A very common, layman's misconception of interpretation is that it is rendered verbatim, that is, as a word-for-word syntactic translation of an utterance. That is impractical, because a literal, verbatim interpretation of a source-language message would be unintelligible to the target-language listener. For example, the Spanish phrase: Está de viaje, rendered verbatim to English translates as: Is of voyage (senseless in English), yet its faithful, true, and accurate denotational and connotational interpretations in context are: ‘He/She/You is/are travelling' or ‘He/She/You is/are out of town'. That is, the overall meaning, tone, and style in the target language are what matter, rather than the source-language syntax.

Interpretation is also held to a different standard of accuracy than translation. Translators have time to consider and revise each word and sentence before delivering their product to the client. While interpreters try to achieve total accuracy at all times, details of the original (source) speech can be omitted from the interpretation into the target language, especially if the source speaker talks very quickly, or recites long lists of figures without a pause.