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 deive 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.