In English, sometimes you say "Sorry" to say you're sorry. Can you say "Brón" in the same way?
I think what lechuzaandaluza meant was, previously, it was mentioned that "ta bron orm" meant both "I am sad" and "I am sorry". In English, we shorten the latter to simply "sorry". Although, I don't think you can shorten "ta bron orm" to just "bron". I don't think it works like that.
'I am sad' is the best translation, but it literally means 'sorrow is on/at me'. 'Brón' isn't the adjective 'sorry', but is just the noun, so if you shortened 'tá brón orm' to 'brón', you'd just be saying 'sorrow', and people would think you were clinically depressed.