Ideea este bună.

Because the basic noun is idee = idea, and the definite article -a is added to the end:

• idee = idea / an idea
• ideea = the idea

When -a is attached to idee, you get ideea, so the double e is just the result of that combination, not a typo.

It is pronounced with both vowels sounded: roughly i-de-ea.

In Romanian, the definite article is usually attached to the end of the noun, instead of being a separate word in front of it.

So:

• idee = an idea / idea
• ideea = the idea

That means Ideea este bună literally looks like idea-the is good, but in natural English it means The idea is good.

Because idee / ideea is a feminine singular noun, and Romanian adjectives usually agree with the noun in gender and number.

So:

• bun = masculine singular
• bună = feminine singular
• buni = masculine plural
• bune = feminine plural

Since ideea is feminine singular, the correct form is bună.

Este means is. It is the 3rd person singular form of the verb a fi = to be.

So:

• eu sunt = I am
• tu ești = you are
• el/ea este = he/she is

In this sentence, este links the subject ideea with the adjective bună, just like is in English.

Yes. E is the short, very common spoken form of este.

So both are correct:

• Ideea este bună. = a bit more formal or neutral
• Ideea e bună. = very common in everyday speech

A learner will hear e very often in normal conversation.

The letter ă is a very common Romanian vowel. It sounds like the a in English sofa or about: a relaxed uh sound.

So bună is pronounced roughly BOO-nuh, not BOO-na.

This ă is different from:

• a = a clearer ah
• â / î = a deeper central vowel that English does not really have

Normally, no. In a standard full sentence, Romanian usually keeps the verb to be.

So the normal sentence is:

• Ideea este bună.
• or more commonly, Ideea e bună.

Just Ideea bună would not be standard Romanian as a complete sentence. It might only appear in very special contexts such as notes, headlines, or poetic style.

The normal, neutral order is:

• Ideea este bună.

Romanian does allow some flexibility, but changing the order usually changes the emphasis.

For example:

• Ideea este bună. = neutral statement
• Bună este ideea. = marked or literary; strongly emphasizes good

For learners, the standard pattern subject + verb + adjective is the safest choice here.

The dictionary form is idee.

Romanian dictionaries usually list nouns in the indefinite singular form, so you would look up:

• idee = idea

Then in actual sentences, you may see forms like:

• o idee = an idea
• ideea = the idea
• unei idei = of/to an idea
• ideii = of/to the idea

So if you want to find the word in a dictionary, search for idee, not ideea.

You would say:

• O idee este bună.
• or more naturally in speech, O idee e bună.

Compare:

• Ideea este bună. = The idea is good
• O idee este bună. = An idea is good

So the difference is:

• ideea = the idea
• o idee = an idea