“减低航速”常见的英文表达是 “reduce the speed” 或 “decrease the speed” ，在航海、航空等专业语境里也常用 “slow down” 。例如：
The captain decided to reduce the speed due to the bad weather.（由于天气恶劣，船长决定减低航速。）
We need to decrease the speed to conserve fuel.（我们需要减低航速以节省燃料。）
The pilot was told to slow down.（飞行员被告知要减低航速 。）