Source language (translation)
In translation, the source language is the language being translated from; it is the antonym of the target language, which is the language being translated to. Part of the difficulty in translation arises due to the lexical gap and syntactical differences between the source language and the target language, especially between two languages belonging to different language families.

In many professional settings, the source language is also the translator's second language. In some regions, however, the source language is the translator's first language because not enough people speak the source language as a second language. For instance, a 2005 survey found that 89% of professional Slovene translators translate into their second language, usually English. In cases where the source language is the translator's first language, the translation process is referred to by various terms, including translating into a non-mother tongue, translating into a second language, inverse translation, service translation, reverse translation, and translation from A to B.