"Evening" and "night" are different. Some languages use the same words for both of them. - Chinese (晚安 - wan an) - Indonesian ("Selamat malam!").
I wrote "yes good night" and Duo marked it wrong and said I needed the article "a". Is that true? Or is my problem actually that I put night and it should be evening?
I think that this is a strange correction. But the best is "yes, good evening" anyway.
Night and evening may be interchangable in English, but English is a very loose language.
Czech and other languages are very exact in their own ways.
That's what makes English easier to mash a bunch of words together, out of order, and still be understood. Even German (same roots as English) behind nonsense if not in the correct order or a similar word is substituted
To exemplify what CultureSharked said with this particular case:
To greet somebody in the later parts of the day (no matter how late into the evening/night), always use "dobrý večer".
Use "dobrou noc" (literally - good night) to wish someone a good sleep or when departing in the later parts of the day.
"Dobrý večer" is a greeting. "Dobrou noc" is used when departing and/or wishing someone a good night's sleep.
evening = večer, night = noc, good evening = dobrý večer, good night = dobrou noc
“Yes, goodnight” is corrected to, “Yes, a good night.” My wife, a native speaker, says I’m right. Lol.
except your native wife may not have realized that "dobrý večer" is a greeting when meeting s.o., whereas "good night" (space or not) is said when one is taking leave. hence you cannot mix them. however, when not used as a greeting, "večer" can be "night", except then the spelling cannot skimp on the space.