The word far is compared as farther/further and with the superlative farthest/furthest.
Farther/farthest are physically measurable distances.
...We walked two miles farther today.
...She drove farther on Monday than today.
Further/furthest are not physically measurable.
...This discussion is going no further.
...She carried the relationship further than she had intended.
Happy punctuating!
Margie