The primary word used for a comparison of two things (bigger, older, etc.) is 比 (bǐ). A simple comparison is constructed as X 比 Y SV.
- Ta bi Xiao Ming gao.
- He is taller than Xiao Ming.
Taken literally, this means that he, when compared with Xiao Ming, is tall.
A simple comparison can be negated by prepending 不 to 比:
- Ta bu bi Xiao Ming gao.
- He is not taller than Xiao Ming.