This is the 1439th most frequent Japanese word.
武器
Weapon.
In this sentence, '武器' refers to a tangible, physical weapon used in combat or war.
彼は戦争で新しい武器を使いました。
He used a new weapon in the war.
Here, '武器' is used metaphorically to indicate an advantageous skill or asset.
その知識は彼の最大の武器です。
That knowledge is his greatest weapon.
In this case, '武器' symbolizes literal armaments or tools of battle that are relinquished in favor of peace.