"Shaadh" vs. "Munkar" Hadith

In hadith science , among the branches of weak ahadith are two types classified as "shaadh" (doubtful, shady) and "munkar" (evil). These two types both refer to a hadith that contradicts a well-known strong body of hadith, such as the 18 narrations of a sahaba praying alone with Rasulullah (salallahu alayhi wa sallam) and being instructed to pray on his **right** side, and one narration where the sahaba was instructed to pray on his **left** side (the latter being a munkar hadith). But what exactly is the shade of difference between these two types of hadith?