Will a 1.8 mod work in 1.8.9?

[XenoIntegrate5]

I want to install a mod, but it's for 1.8. I'm using forge 1.8.9 as that is what most of the mods I'm using work with. So I was wondering if I could still use it, or would it not work? If not, then why? How different is 1.8.9 from 1.8 that it wouldn't work?

[Choonster]

Some 1.8 mods may work in 1.8.9, but there's no guarantee that every mod will.

 

1.8.8/1.8.9 didn't change a lot of things, but there were a few minor changes that will break some 1.8 mods.