Adapted from r.chriss.Comcast.net

The True Professional:  There are translators and then there are professional translators: the former are people who translate on the side, using their knowledge of a particular field to translation work (for example, a mathematician who translated a book on advanced mathematics).  Professional translators are applied linguists whose ability to work with language, write well, and for freelancers, to operate a business, represents their source of income. 

Professional translators are people who are dedicated to their languages and the nations, societies, and cultures which come with them.  They are devoted to improving their ability to understand their source language and write in their target language.