What is the word when you want to say the road a plane runs before taking off.
Hi. The word is "runway".

Your question could have been improved as follows:-

"What is the word for the road that a plane uses when taking off?"
Tarmac is a word used to describe the actual surface of the runway.
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Tarmac is actually a trademark and it sounds pretty technical to me and refers to the paving material used on the surface of a road or a runway. Runway is a common word. What if the runway does not have a tarmac layer? Emotion: smile

It's similar to "shaving blade". Some people in my country still call them "guillette" because it was the first brand commercialized. Emotion: smile
Raul, don't you mean Gillette? Other examples are Hoover for vacuum cleaner and Thermos for vacuum flask.

Tarmac is an abbreviation for Tarmacadam which was invented by John McAdam.
Yes, you're right. I didn't remember the spelling... I use another brand. Emotion: smile

Thermos is a great example, nobody says vacuum fask. We do say vacuum cleaner, but some of us still say "Frigidaire" for refrigerator, for instance. Kolynos is a funny example. Typical dialog at the corner store:

A: Give me a Kolynos, please.
B: What brand?
A: Crest, please

Tarmacdam? Tar MacAdam... very, very smart name. Emotion: wink
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There are two things going on here. The runway is the surface a plane actually lands and takes off from. There is also the taxiway (taxi way) which is the road a plane uses to get from the terminal to the runway.
CAO What is the word when you want to say the road a plane runs before taking off.
In some contexts you'll also see airstrip.