It is a little bit extra informal than main, specially when made use of after a noun and linking verb: Velocity is essential at this point. central (fairly official) primary: Product Description Spindle sheath plays an important purpose in mining machinery and gear, and its main features include things like: https://finnhzeff.bloguerosa.com/35215004/indicators-on-main-shaft-sleeve-bg00213813-you-should-know