Grammar: farther or further?
It is a complete myth that farther differs in meaning from further. The myth persists more in American English than British English. Further is the spelling to be preferred in all contexts, including distance and physical position. The same applies to furthest and farthest. Of this pair, only question mark remains: how has farthest survived this long as a legitimate word?
Farther began life in the 1100s as a variant spelling of the Old English word furþur (further) when farrer and ferrer were used as comparatives of far. By the 1600s ferrer and farrer had died off as forms existing only in regional dialects. Farther had muscled in on these two words and ultimately survived, still as a variant spelling of further only, right through Shakespeare's time (he preferred further four-fifths of the time) to the late 1800s. It was at this point that the idea of farther meaning "distance, movement, position" arose. This was wrong.
So what does this mean? It means that you can drop farther from your vocabulary. Further and farther mean the same thing – and further is the standard spelling in both British and American English. Use the variant spelling if you must but the choice is stylistic rather than one of meaning, like the choice between jail and gaol.
About the author
Jesse Karjalainen is the author of The Joy of English: 100 conversations about the English Language, Cannibal – the language and history of the discovery of the New World, and Roanoke – the language and history of Early Colonial America.