• 制度せいど — system, institution
• 制限せいげん — restriction, limit
• 制御せいぎょ — control, management
• 制作せいさく — production, creation
• 強制きょうせい — compulsion, enforcement
• 法制ほうせい — legislation

制 combines the components 刀 (knife) and 未 (not yet / tree branch), suggesting “cutting or limiting what is not yet formed.” It conveys control, regulation, and enforcement, often in political, educational, or industrial settings.

速度そくどを 制限せいげんしてください。
Please limit your speed.

新あたらしい 制度せいどが 始はじまりました。
A new system has been implemented.

The onyomi “セイ” is the only commonly used reading and appears in all compounds such as 制度せいど, 制限せいげん, and 制御せいぎょ. There is no commonly used kunyomi in modern Japanese.