Soldiers who fight on foot (on land), as opposed to cavalry and other mounted units, regardless of external transport (e.g. airborne).
"The infantry charged across the open field while the cavalry held back in reserve."
In plain English: Infantry is soldiers who fight on foot instead of using vehicles or aircraft.
"The infantry marched through the muddy field toward the front lines."
Usage: Infantry refers specifically to soldiers who engage in combat while moving primarily on their own two feet across the ground. This term distinguishes them from armored or mechanized troops that rely heavily on vehicles for movement during battle.
The word infantry comes from the Middle French infanterie, which was borrowed from Italian and possibly Spanish to describe foot soldiers or those too inexperienced for cavalry. Its root lies in the Latin īnfāns, meaning "child," reflecting an original sense of youth before evolving into its current military definition.