Is there any difference between farther and further? Merriam-Webster’s online dictionary notes in a usage discussion that as an adverb, farther and further are used indiscriminately when literal or figurative distance is involved:
“How much farther do we have to go?”
“It’s just a mile further.”
“How much further do you want to take this argument?”
“I’ve taken it farther than I want to already.”
However, in adjectival form, a distinction has developed regarding use in these senses:
“My house is the farther of the two.”
“She needs no further introduction.”
But dictionaries are descriptive; they describe not how people should use language, but how they do use it. However, language maven (and therefore prescriptive) Bryan A. Garner, in Garner’s Modern English Usage, advises, “In the best usage, farther refers to physical distances, further to figurative distances,” and I agree: Popular usage demonstrates just that — popular usage — and the careful writer maintains distinctions that enrich the language. (Write eager when you mean eager, for example, and anxious when you mean anxious.)
Farthest and furthest, by extension, should maintain the same distinct meanings; use these forms in favor of the burdensome farthermost and furthermost. Furthering and furtherance are interchangeable noun forms that serve as synonyms for promotion or advocacy; there is no equivalent noun form for farther.
Further is also employed as a modifier, as in “Further, I see no reason to delay the proceedings”; furthermore is a variant. Farther, however, does not fit this role.
This Daily Writing Tips post from a former contributor has a somewhat different take; as always, consider what you read here (and there) a springboard (or two) for farther — I mean further — research to help you make up your mind about how you write.