Water content or moisture—amount of water contained in something (e.g., juiciness of food, dampness).
肉は焼く前に余分な水気を拭き取ってください。
Please wipe off excess moisture from the meat before grilling.
果物は水気が多いと日持ちしにくい。
Fruits with high moisture content don't keep well.
タオルの水気をよく絞ってから干してください。
Wring the towel well to remove moisture before hanging it to dry.
Water vapor or steam—moisture present in the air as vapor (e.g., steam from hot water).
朝、窓に水気がついて外が見えにくかった。
In the morning the window was covered with condensation, making it hard to see outside.
風呂場はすぐに水気がこもる。
The bathroom quickly fills with steam.
Dropsy/edema—the medical condition of excess water accumulating in the body (swelling).
医師は足の水気（むくみ）を確認して治療を始めた。
The doctor checked the swelling in the patient's legs and began treatment.