das Gas
gas
A flammable gaseous substance, especially natural gas, used for heating, cooking, or as fuel.
Die neue Wohnung hat eine Heizung, die mit Gas betrieben wird.
The new apartment has a heating system that runs on gas.

gas
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gas
A flammable gaseous substance, especially natural gas, used for heating, cooking, or as fuel.
Die neue Wohnung hat eine Heizung, die mit Gas betrieben wird.
The new apartment has a heating system that runs on gas.

Careful: 'das Gas' (gas) is not the same as the English 'gas' (gasoline). 'Gas' in Germany usually means natural gas for heating or cooking. What you put in a car is 'das Benzin' (gasoline/petrol).
Im Winter sind die Kosten für Gas immer am höchsten.
In winter, the costs for gas are always highest.
When 'Gas' (gas) means fuel for heating, it is almost always used in the singular as an uncountable noun. The plural 'die Gase' (gases) usually refers to different types of gases in chemistry or physics.
Wir müssen diesen Monat eine hohe Rechnung für Gas bezahlen.
We have to pay a high bill for gas this month.
In everyday life, 'Gas' (gas) is often used in fixed combinations related to heating and cooking, for example 'der Gasherd' (gas stove), 'die Gasheizung' (gas heating), or 'der Gaszähler' (gas meter).
Viele Köche bevorzugen einen Gasherd, weil man die Hitze besser regulieren kann.
Many cooks prefer a gas stove because you can regulate the heat better.
The expression 'Gas geben' (to accelerate / to step on it) means pressing the gas pedal in a car and speeding up. Colloquially, it is also used to say that someone should hurry up or make more effort.
Die Ampel ist grün, gib Gas!
The light is green, step on it!
air
'die Luft' and 'das Gas' are related because air consists of gases. Still, the words are not used in the same way. 'die Luft' normally means what we breathe outside or in a room. 'das Gas' more often means a specific gaseous substance, for example in chemistry, in heating, or when something may be dangerous. Learners may confuse the words because air is also a mixture of gases. In everyday language, however, you say 'frische Luft' (fresh air), 'schlechte Luft' (bad air), or 'Luft zum Atmen' (air to breathe), not simply 'Gas'.

Im Labor prüft die Lehrerin, ob das Gas gefährlich ist.
In the lab, the teacher checks whether the gas is dangerous.
Im Park ist die Luft heute besonders frisch.
The air in the park is especially fresh today.