"Mężczyzna nie jest dzieckiem."

Translation: A man is not a child.

[Denise763738]

Depends on the man, actually...I've met more than a few ...

[HerrEktor]

I would argue ...

[999Road]

why dzieckiem instead of dziecko?

[va-diim]

Objects after the verbs jestem, jesteś, jest, jesteśmy, jesteście, są, etc., decline to the instrumental case.

[alik1989]

Welcome to Polish cases :)

https://forum.duolingo.com/comment/16373167

[999Road]

Polish is so hard and i have two months to learn enough to be able to speak it and understand what polish people say....

[alik1989]

I'm sorry to say this, but I don't think 2 months are enough, unless you are some kind of language genious and spend 12 hours a day learning Polish.

[999Road]

Im actually doing that since two days ago xD

[VioletInLA]

why is the translation wrong if I did not use an 'a'? I answered 'Man is not a child'.

[va-diim]

Because "man" means "mankind." "A man" is just mężczyzna

[michael.za2]

Why is dzieckiem in narzędnik? Wouldn't its negation cause it to be dopełniacz?

[Vengir]

Not all cases behave like that. Instrumental stays instrumental.

[Mlini25]

Wrote mam instead of man and my answer was wrong?

[Jellei]

What's the question? You didn't write the correct word. I understand it was just a typo, but we have no power over what gets 'accepted with a typo' and what is just rejected.

[Aleks778302]

so basically after jest or jestem I have to chose the extended version of the word?

[va-diim]

You have to use the instrumental case of the noun and its adjectives, after jestem/jesteś/jest/jesteśmy/jesteście/są.

Different cases are not extended versions of a word. They're just cases. Some cases shorten the word.