1.  (I) will;  (I) shall
on non-五段 stem, e.g. 食べる→食べよう; indicates intention
2.  let's
on non-五段 stem; indicates suggestion or invitation
3.  (I) wonder (if);  might it be (that);  maybe;  perhaps;  perchance
on non-五段 stem; indicates speculation
Interjection
Familiar language
4.  hey;  yo;  hi
5.  come on;  hey
empathetic version of よ