Bien is an adverb, so it's used much as English uses well.
Buen is the shortened form of bueno that's used right before a masculine singular noun: un buen libro (a good book) but este libro es bueno (this book is good).
(With my normal caveat that I'm not a native speaker, and Anna will have the definitive answer! But I think that's more or less the story.)
Bien is an adverb (meaning well) and buen is an adjective (meaning good)
- Lo hiciste bien. (You did it well)
Buen is used in from of a masculine noun, while bueno/a is used after the noun:
- Fue un buen viaje. (It was a good trip) - El viaje fue bueno. (The trip was good)
As a general rule, adjectives generally go after the noun, and the sentence will have a more literal meaning. When coming before a noun, an adjective generally takes on a more figurative, poetic, or literary sense.
I have another question along these lines. When someone wants to say "that's good", or "that's OK" I will sometimes hear "esta bien" and sometimes "es bueno." What is the difference? When do you use one or the other? I understand that bien describes a verb and buen/bueno describes a noun.
Mahima you are right about using ser or estar for permanent qualities or temporary qualities. Another student asked a similar question in the Spanish Forum and I wrote a quick guide on when to use SER or ESTAR.
Comments
- El viaje fue bueno. (The trip was good)
As a general rule, adjectives generally go after the noun, and the sentence will have a more literal meaning. When coming before a noun, an adjective generally takes on a more figurative, poetic, or literary sense.