• 火ひ — fire
• 火山かざん — volcano
• 火事かじ — fire (incident)
• 火曜日かようび — Tuesday
• 花火はなび — fireworks
• 火照ほてる — feel hot / flush

The character 火 is a pictograph showing flames rising upward. It represents not only physical fire, but also ideas such as danger, passion, and energy in Japanese expressions.