The definition of farther is more distant or additional.(adjective)
An example of the use of farther as an adjective is in the sentence, "The blue house is on the farther side of the street," which means the blue house is not as close as the brown one.
Farther is defined as to a greater extent or distance.(adverb)
An example of farther used as an adverb is in the sentence, "The pink coffee mug was placed farther away than the green one," which means that the green coffee mug is closer.
See farther in Webster's New World College Dictionary
Origin: ME ferther, var. of further, substituted for regular ferrer (compar. of fer) < OE fyrre, compar. of feorr, far
See farther in American Heritage Dictionary 4
adverb A comparative of far.
Origin: Middle English
Origin: , variant (influenced by far, far)
Origin: of further; see further. Usage Note: Since the Middle English period many writers have used farther and further interchangeably. According to a relatively recent rule, however, farther should be reserved for physical distance and further for nonphysical, metaphorical advancement. Thus 74 percent of the Usage Panel prefers farther in the sentence If you are planning to drive any farther than Ukiah, you'd better carry chains, and 64 percent prefers further in the sentence We won't be able to answer these questions until we are further along in our research. In many cases, however, the distinction is not easy to draw. If we speak of a statement that is far from the truth, for example, we should also allow the use of farther in a sentence such as Nothing could be farther from the truth. But Nothing could be further from the truth is so well established as to seem a fixed expression.
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