A constructive discussion, comment, or approach is useful and helpful rather than negative and unhelpful.
例句
She welcomes constructive criticism...她歡迎建設性的批評。After their meeting, both men described the talks as frank, friendly and constructive...會面之后，兩位男士均形容此次會談坦率、友好且富有建設性。
英英詞典釋義
Adverb
1. in a constructive manner;
"it is my task to look critically and constructively at the flaws and the failures"