"An elephant is big."
Translation:हाथी बड़ा होता है।
Duolingo accepted हाथी बड़ा है without होता. Is this just a mistake or is both correct? I guess I still do not understand this completely - as far as I understand the construction with होता is for sentences with a generell meaning like Elephants are big animals (in generall). Could someone please explane to me? Thank you in advance!
Both are correct depending on what you want to convey.
As you say, होता is used when you're making generalisations. So, the sentence हाथी बड़ा होता है। is saying that elephants, as a species, are big animals. In English, we would usually use the plural form 'Elephants are big' to say this but both the singular and plural (हाथी बड़े होते हैं) forms are interchangeable in Hindi.
'हाथी बड़ा है' may be 'An elephant is big' which is talking about any odd elephant and is not a general statement about the whole species. However, because Hindi does not have a definite article, it may also mean 'The elephant is big' which is talking about some particular elephant. Which of these meanings it should be understood as comes down to context.