Water vapor produced by heating (steam); vapor used in contexts like steam and steam-powered machinery.
やかんから白い蒸気が勢いよく上がっている。
White steam is rising vigorously from the kettle.
蒸気で手をやけどしないように気をつけてください。
Be careful not to burn your hand with steam.
工場では蒸気を使って機械を動かしている部分がある。
Some parts of the factory use steam to power machinery.
An abbreviated usage referring to steamboats or steam locomotives; in context it can mean steam-powered ships or trains.
昔は蒸気が交通の中心だった（蒸気船や蒸気機関車が活躍した）。
In the past, steam was central to transportation (steamboats and steam locomotives were active).