could you tell me about difference of further and farther, older and elder, furthest and farthest, oldest and eldest.
Thank you very much for reading and answering me.
The difference between farther/further (and farthest/furthest) is discussed in the usage note here:
As for the difference between elder and older (and eldest and oldest), you could start with this link:
english-test.net/forum/ftopi … html#57479