Questions & Answers about Dat is een beter idee.
Where does the word beter come from?
Just like in English (where "good" becomes "better"), the Dutch word goed (good) has an irregular comparative form: beter.
Why isn't there an -e at the end of beter, like een betere idee?
Adjectives usually get an -e added to them. However, idee is a het-word (het idee). When a het-word follows een (a), the adjective before it does not get the extra -e. So it stays een beter idee.
How would I say "That is the best idea" using this sentence structure?
You would say Dat is het beste idee. The highest degree (superlative) of goed is best. Because we are now using the specific word het instead of een, the adjective gets its normal -e ending: beste.
Why does the sentence use Dat instead of Die for "That"?
We use dat because idee is a het-word. If you were pointing to a de-word, you would use die instead.