Blesta uses a single language file to store both client and admin side language. Language files are located in the /language/ directory.
The naming convention uses both the ISO 639 and ISO 3166 standards. That is, a 2-digit language code followed by a hypen (-) then the 2-digit country code (i.e. en-us.php for US English). This naming convention allows differentiation between various dialects. For example, English spoken in the United States of America (en-us) is much different than that of English in the United Kingdom (en-gb). Similarly, Spanish spoken in Spain (es-es) differs from that of Spanish in Mexico (es-mx).
A language validator is provided to help with translatating various versions of the language file. This tool identifies missing and unnecessary language defines in your language file, which may be difficult to determine otherwise.
Visit our forums to find various language contributions, or to contribute your own translation.