There are numerous definitions of translation, depending on the perspective adopted. Here I shall suggest a simple and practical definition:

Translation is an interlingual communicative activity that is performed by a particular individual (with his/her own specific ideology, motivation, etc), in a particular place, at a particular time, for a particular reason.

You should always remember that translation does not happen in a vacuum. Professional translators do not just 'translate'. They are engaged in a process that involves the following participants:

• Initiator/commissioner: this is the person who needs the translation for a particular reason. The main aim of the translator is to fulfil their request, which is usually specified in a brief.
• Source text, source language (ST, SL): text that forms the basis of the translation activity; text/language from which we translate.
• Translator: may be an individual or a team.
• Target text, target language (TT, TL): text/language into which we translate; text produced as a result of a translation activity.
• Target text receiver: receptor of the target text (may or may not coincide with the target text user).
• Target text user: user of the target text (may or may not be the same as the target receptor).

(Source: Nord, 1997)