"They are not short."
I think if you use "oni," it would have to be "Oni nejsou krátcí" to be correct... I got this one wrong too.
Because Duo makes a mistake in defining ONA as they. ONA is she. ONI is they, so you are right. krátká in the same sentence with nejsou is wrong too, this adjective serves for singular nouns; it should be krátcí or krátké in the same sentence with ONI, if nejsou is used for the verb. I noticed so far many more mistakes of the kind. Maybe it is done here this way for the sake of simplicity at the beginning of the course, but grammatically it is wrong and confusing.
Nominatives in -a can be either neuter plural or feminine singular. So, the "ona" here is the plural of "ono".
Krátká can also be neuter nominative plural of krátký.
"Neut pl sounding like fem sg" is similar to Latin.
ONA is (also) THEY. There is nothing wrong at all here. The simple English they can have three different genders in Czech. You cannot single any of them out.
This word order is a bit puzzling. I parse it as: "Those short ones aren't"?
What exactly is the difference in Czech between:
Ona nejsou krátká
Ona krátká nejsou.
You usually put the word you want to stress at the end of the sentence.
Ona nejsou krátká. = 'They are not SHORT.'
Ona krátká nejsou. = 'They ARE NOT short.'
I see, thanks. I suppose there is also a possibility of using different intonation to achieve the same without reordering the words. Would you say that the first example is also the neutral one, when you are not stressing anything in particular?
The English sentence provides no information about gender, so there are many acceptable translations. "Oni nejsou krátcí" is one of them.
Is there a good way to tell that "they" are feminine (On vs Ona)? As a native English speaker, I don't necessarily understand why we would use one or the other.
In this case, ona refers to neuters. (Ono - singular, ona - plural)
How do I know that? Look at the ending of krátká, it's -á, so it's a neuter.
You can tell the difference from the endings of the corresponding words (krátcí vs krátké vs krátká) or sometimes from the ending of the verb, but that's more complicated and I don't really want to get into that (it's connected to the past tense and participles and it's not something for complete beginners).
Unfortunately, sometimes you have to glean it from context.
"Nejsou" is plural. "Ona" and "krátká" can be either feminine singular or neuter plural, but the verb would be "není" if it were singular.
English - They are not short. I wrote: Ona nejsou krátká. It was marked wrong and the correct was: Krátká nejsou. They are both the same.
"Ona nejsou krátká" is an accepted translation. Perhaps there was something else in your answer that Duo didn’t like. For troubleshooting, it’s best to either (1) use the report button in addition to commenting, or (2) include a screenshot in your comment, so that the team can see your complete answer. (Reporting is easier.)
You have a gender mismatch between the pronoun and the adjective; oni is masculine animate and kratké is masculine inanimate or feminine. If you want to use oni, the correct translation would be "Oni nejsou krátcí."
The to je/je to/to jsou/jsou to only works if you say that something is some object, some noun phrase. Without the object it simply does not work.
For example: To nejsou krátké dny. To nejsou krátké holky. But without the noun it is just nonsense.