das Casino
casino
A public building or room where games of chance are played for money; a gambling house.
Am Wochenende haben wir im Casino unser Glück beim Roulette versucht.
At the weekend, we tried our luck at roulette in the casino.

casino
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casino
A public building or room where games of chance are played for money; a gambling house.
Am Wochenende haben wir im Casino unser Glück beim Roulette versucht.
At the weekend, we tried our luck at roulette in the casino.

You can easily recognize the meaning of 'Casino' from the context. If it is about gambling, money, roulette, or poker, it means a casino. If it is about lunch, employees, a company, or the military, it means a dining hall.
Er hat beim Pokern im Casino viel Geld gewonnen.
He won a lot of money playing poker in the casino.
As with many buildings, you use 'ins Casino' (accusative) for direction and 'im Casino' (dative) for location. This applies to both meanings of the word.
Wir gehen heute Abend schick angezogen ins Casino.
We're going to the casino tonight dressed up smartly.
When referring to the gambling house, typical expressions are 'sein Glück versuchen' (to try one's luck), 'Geld verspielen' (to gamble away money), or 'einen Croupier beobachten' (to watch a croupier).
Manche Leute verspielen im Casino ihr ganzes Vermögen.
Some people gamble away their entire fortune in the casino.
cafeteria
'das Casino' and 'die Mensa' can both mean a dining hall, but they fit different settings. 'Mensa' is used especially at a university or school, where students, pupils, or staff eat cheaply. 'Casino' can mean a dining hall for a specific group in certain companies or in the military. This 'Casino' has nothing to do with gambling, although the word can also have that meaning. The words can be confused if you are only thinking of a place to eat. For universities and schools, 'Mensa' is almost always the natural word.

Im Casino der Firma essen die Mitarbeiter jeden Mittag zusammen.
The employees eat together every lunchtime in the company's dining hall.
Zur Vorbereitung auf die Prüfung trifft Ida ihre Lerngruppe nach dem Essen in der Mensa.
To prepare for the exam, Ida meets her study group in the cafeteria after lunch.