I. -ˈsīd adverb
Date: 1707
1. : along the side : in parallel position
2. : at the side : close by
a guard with a prisoner alongside
II. preposition
Date: 1776
1.
a. : along the side of
the boat docked alongside the pier
b. : beside 1
standing alongside me
2.
a. : in company with
men she has been working alongside — Richard Halloran
b. : in addition to
a special category alongside the awards it annually presents — Horizon