[Haskell-beginners] It needs a binder?

Hi, binder.hs i:: Num a => a prelude>:l binder.hs typed_checked.hs:1:1: error:     The type signature for ‘i’ lacks an accompanying binding   | 1 | i:: Num a=> a   | ^ binder.hs i:: Num a => a i = 2 prelude>:l binder.hs [1 of 1] Compiling Main              Ok, one module loaded. Why does it need a binder to make it work?