Equality & Inequality

Given the following expressions:

extent  >  height
honeybee  <  kitten
antenna  >  backbone
money  =  stone

Then what comes in the following blank?

freight < [ ] < pretender

Answer (7 letters or shorter):

*Inspired by: Ichimai Quiz featuring tb_lb

As you see, they're mathematical expressions.

If you think the answer cannot be identified uniquely,
then... well it's a top secret :P