Some of the adjectives compare irregularly. You should remember their comparative and superlative form:
|the furthest(the farthest)
She’s better at maths than me.
It’s the best film I’ve ever seen.
It was the worst experience of my life!
Have you got any further news?
Adjective “old” is usually compared regularly:
Tom is older than me.
The alternative form elder/eldest shall be used in the descriptions of family members.
Forms elder/eldest can be used only before a noun. We can not use elder/eldest in comparisons.
Farther and further can be used in sentences referring to distance:
It’s so dark that I can’t see farther/further than a metre.