Wiktionary
n. (lb en usually uncountable) criticism intended to provide suggestions for improvement without insulting the recipient.
Wikipedia
Constructive criticism is the process of offering valid and well-reasoned opinions about the work of others, usually involving both positive and negative comments, in a friendly manner rather than an oppositional one. The purpose of 'constructive criticism is to improve the outcome. In collaborative work, this kind of criticism is a valuable tool in raising and maintaining performance standards.
Usage examples of "constructive criticism".
It was sound, constructive criticism, with no motive behind it but the kindly desire to keep her from making an exhibition of herself in public.
He felt that they were at ease, and from such mental relaxation would frequently come a sound suggestion, or a constructive criticism, which would be stillborn, stifled in a more formal talk.
Alas for the world, we now no longer know which eager young writer will take constructive criticism as an invitation to assassination.
We are here to serve, and, of course, we're always interested in constructive criticism from the taxpayers.