'Zure' before a 'de-woord'
'Zuur' before a 'het-woord' (when it's preceded by 'een' or no other determiner).
They do exist where I lived in Costa Rica. We call them exactly that, "sweet lemons".
Haha thanks, it's been a long time since i've used duolingo and i wanna get back into learning lol. But thanks for the help
Adjectives normally get the 'e' except in the case of indefinite article 'een' in front of a 'het' 'noun. Citroen is a 'de' noun, so 'zuur' becomes 'zure'.
If I understand correctly, you can drink either 'een zure wijn' or 'een zuur bier'.