Recommended by Erick
"FARTHER" and "FURTHER"
"Farther" refers to physical distance. "Further" relates to metaphorical or non-physical distance. Ex.: The park is farther than I thought. We need to look further into this issue.
"ALTOGETHER" and "ALL TOGETHER"
"Altogether" means completely or in total. "All together" means everyone or everything in a group. Ex.: The project was altogether successful. We sang the song all together.