“Thomas the Apostle went east, though what is now Syria and Iran and, historians believe, on down to southern India. He traveled farther than even the indefatigable Paul, whose journeys encompassed much of the Mediterranean. Of all the Apostles, Thomas represents most profoundly the missionary zeal associated with the rise of Christianity—the drive to travel to the ends of the known world to preach a new creed.” –National Geographic
Further and farther are used to refer to distance in space, direction, or time and both the words function as adjectives and adverbs. These two words are used interchangeably in the sense of distance. But further differs from farther, which is, further also means more: further means additionally, in addition to.
FARTHER: Farther as an adjective means more distant things in terms of space, direction, time, degree.
Example: Iran is farther from India than Pakistan, Bhutan, Bangladesh and Nepal.
Farther functions as an adjective and adverb; a comparative of the adjective ‘far’- far, farther, farthest: most distance in space, direction, time; longest, most extended in space. Example: The farthest planet to Earth is Neptune (2.7 – 2.9 billion miles away).
Farther as an adverb is a comparative of the adverb ‘far’: at or to a greater distance in space or time; more remote. Example: Can we go any farther without resting?
Far afield & farther afield is an idiom.
Farther as the superlative of far (adverb) refers to the greatest distance in space or time, most remote, to the highest degree or extent. Example: Who among the class is the farthest advanced student?
NOTE: ‘Further’ is common than ‘farther’ in British English. In US English farther is usually used in relation to distance. They are used in relation to distance. Which means further and farther are used interchangeably in this sense (distance). Furthest or farthest refer to distance. Examples:
I can throw the stone much further/farther than you.
From Delhi, Hyderabad is further/farther than Nagpur.
The farthest (or furthest) planet to Earth is Saturn. In US English farther is usually used in relation to distance.
“And in 1998, to further financial journalism, she (Marjorie Deane, died at the age of 94) set up a foundation in her name whose editorial internships and student grants are much sought after.” –The Economist
FURTHER: Further has another meaning which is more, to indicate addition. Further as verb means to promote something, to support, or aid, or help the progress of something, someone. Examples: Are there any further questions, audience? A College of Further Education will prepare a student for the University life. To further the cause of peace is one of the objectives of the United Nations. Example: Further (adjective) education is important, some travel further to achieve it.
The usage of further as a verb – “An Artist in Flux,” The Sunday Indian Express 5 May 2013. “A London exhibition pays tribute to Lancelot Ribeiro who furthered Indian art in Europe before others but has been overshadowed in India by his famous half brother.”
Furtherance (n) means advancement of somebody’s interests, or a cause.
Furthermore (adverb) means in addition, moreover.
Furthermost (adjective) means most distant in space, time, furthest
Furthest or farthest also refer to distance.
“Wading birds from Iceland and farther north that have finished nesting are beginning to appear here on their way south.” – The Times (London)
“And in 1998, to further financial journalism, she (Marjorie Deane, died at the age of 94) set up a foundation in her name whose editorial internships and student grants are much sought after.” – The Economist 11 October 2008.
Farthing was part of British coinage (one quarter of a penny) which is no longer in use but an idiom is in usage: give a farthing which means ‘not care at all’. Furthermore?