"Eating sugar is a bad idea."
Translation:Jedzenie cukru to zły pomysł.
No, it is not.
1). As general rule, the negation "nie-" is written together with adjectives and with adverbs created from adjectives in their basic form (initial degree): adjectives: niedobry, niesmaczny, nieładny, niebrzydki, niewystarczający, niedrogi ; adverbs: niedobrze, niesmacznie, nieładnie, niebrzydko, niedrogo, nietrudno.
There are some exceptions, but the above is not one of them. "Nie" is writen separately when:
- An adjective with "nie-" is an introduction to contraposition: "nie zły, ale dobry" [not bad, but good]
- An adjective in basic form with "nie-" introduces adjective in comparative or superlative: "nie zły, a gorszy" [not bad, but worse]
- The basic adjective is written with a capital, "nie" is separated by a hyphen: nie-Szekspirowski [not Shakespearian]
- Other exceptions here.
2). Negation "nie-" is written separately with adjectives in comparative and superlative, but there are also some limited exceptions.
Are you sure that those are the words that you meant? The question makes sense, but given the sentence here it also seems probable that you meant "pomysł". Just checking.
If we were to compare "myśl" and "pomysł", it's pretty easy: a thought vs an idea.
If you really meant "myśl" and "pomyśl", those are the 2nd person singular imperative forms of "myśleć" and "pomyśleć" respectively. In imperative it will be mostly "pomyśl", something like "think about it!" or maybe "give it a thought!"; "myśl" will be rather less common, although I can imagine for example "Myśl czasami!" (Think sometimes! = Geez, turn your brain on sometimes, moron!)
Easier to show the difference in the Past Tense: "On myślał, że ona go nie kocha" (He thought that she doesn't love him; simple as that) vs "On pomyślał, że ona go nie kocha" (Suddenly a thought that she doesn't love him appeared in his mind).
You do not say that in Polish. "idea" in Polish is something very abstract and of wide influence:
- A general theme that sets the objective of activity, scientific research, artistic tendencies.
- A belief, paradigm or attitude that is characteristic for given epoch, culture or social group.
- An impression of human mind that is the subject of recognition
+ some special meanings in platonism and philosophy of Immanuel Kant.