Soldier, Military Personnel
noun
An army person is someone in the army. What are those people called? They're soldiers.
ぐんじん
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
うちの父は元軍人です。
My father is a former soldier.
見て、あそこに軍人さんがたくさんいる。どうしたんだろう？
Look, there are a lot of servicemen over there. I wonder what's going on?
その戦争では、50万人以上の軍人が命を落としました。
In that war, over 500,000 servicemen lost their lives.