I would say that knit and gnome are similar in that both words have a silent letter/sound: in knit, you don't read the K sound in the beginning, and in gnome, you don't read the G sound in the beginning. Other than that, I don't really see many similarities between those two words. When it comes to differences, the obvious one is the meaning - they don't mean the same thing. Also, knit is a verb, whereas gnome is a noun. They are also spelled differently, because they are different words, and so on. Hope this helps! =)
