In Greek for the world is a genitive expression, literally “of the world,” but the preposition for expresses the meaning more clearly. Moffatt translates this verse in the same way. In some languages I am the light for the world may be rendered “I am the one who causes light for people in the world.” It is important to avoid a literal translation which would suggest that Jesus is the sun.

Quoted with permission from Newman, Barclay M. and Nida, Eugene A. A Handbook on the Gospel of John. (UBS Handbook Series). New York: UBS, 1980. For this and other handbooks for translators see here .