• 剣つるぎ — sword
• 剣道けんどう — kendo
• 真剣しんけん — real sword; serious
• 刀剣とうけん — swords and blades
• 短剣たんけん — dagger
• 剣先けんさき — sword tip

A classic phono-semantic build: the left side 刂 marks the blade set; the right side (from the old form 劍) contributes sound and the idea of a double-edged weapon. That is why words with 剣 often relate to martial arts or edged tools (剣道, 短剣, 真剣).