• 常々つねづね — always / usually
• 常識じょうしき — common sense
• 非常ひじょう — emergency / unusual
• 通常つうじょう — usual / normal
• 常温じょうおん — room temperature
• 常時じょうじ — at all times
• 常連じょうれん — regular customer
• 常夏とこなつ — eternal summer

常 is a 形声 (keisei) character, combining 巾 (cloth) for meaning with phonetic elements. It conveys the idea of something steady or laid out flat, extending to “usual” or “constant” in modern Japanese.