1.Compare vs contrast
Compare: discuss the similarities between two or more items/issues.
Contrast: contrast comes from the Latin root contra, and means "against".discuss the differences between two or more itens/issues.
Compare is to identify similarities or differences between two objects; contrast is to only find the differences.
2.Sign up vs Log in
Sign up / Register ： 注册 （网上提交注册到服务器）
Log in： 登录 （登录进去，使用软件，计算机术语）
Sign in：登陆（生活用于，同Log in）