When do you use "buen" instead of "bueno"?

Question

"un buen medico" but "un medico muy bueno". When do you use "buen" instead of "bueno"? Thank you!

Answer 1

In front of masc. sing. nouns.

Answer 2

You drop the vowel "o" when the singular masculine adjective precedes the verb. Note that changing your example to the plural would be "Los buenos medicos," Usually it is "Buenos días" but in some countries they use the singular "buen día."

Answer 3

you can say something bueno if that something is a masculine singular, and you can alternatively say buen something if that something is a masculine singular. you drop the o when you put it in front only if it's singular and masculine.