Translation:What is the color of your new door?
How do we know that door is singular in that sentence if the word is always plural?
Door is plural. Even in the sentence above. The verb JE is referring to its color, which seems to be only one on them.
I think Fabien was asking: how do we know if "dveře" is to be translated as "door" or "doors in English? If the word is always plural in Czech, how can we count doors (one door, two doors... etc.)? Her house's door : dveře její domu Her house's doorS (as in "both the front door and the back door") : ?
For me, Duo accepted "what is the color of your new doors" unlike the main translation. Assume either singular or plural is acceptable if no context to tell which is correct?
While dveře is always plural in Czech, in English, it can be either "door" or "doors." If there is no clear context, there is no way to know how many "doors" are being discussed, and both singular and plural are accepted.
Similar to the English word “pants”. “What color are your new pants?” would be the same question if you’re asking about one pair of new pants or five pairs of new pants. I believe the Czech word for pants - kalhoty works the same way.