Hi there!
Many students struggle to understand the difference between these two couples of words:
Which are the main differences?
- Bien and Mal are adverbs. They follow a verb. For example:
"Yo estoy bien", "Ellos están mal".
And note that they do not need gender neither number concordance with subject or object. They only have one way to be written in any case, "bien" and "mal".
- Bueno and Malo are adjectives. They follow a noun. For example:
"Él es alto", "Ella está contenta", "Ellos son altos", "Ellas están contentas".
In this case, they need to have gender and number concordance with the subject / object, as they are adjectives. So you have these four forms: "bueno", "buenos" and "buena", "buenas".
Here is an additional short explanation that may help you.
And here another one! It also talks about the adjective form "buen" and the adjective "grande", which works similarly.
Hope this helps. Thank you for reading ! :)
