An infantryman is a soldier whose job is to fight on the ground, on foot. He is not the person in the tank, in the plane, or on the ship: he walks, carries a gun, and takes land. Armies still talk about “the infantry” as a whole group; infantryman names one person in that group. The word sounds a little old or official. In easy talk people often just say a soldier, or an infantry soldier. Though actually, in today’s armies many infantry soldiers also ride in vehicles — the name still marks the ground job, close to the enemy, not fighting from the air or the sea.