Is there a difference between deadweight loss and welfare loss? I've heard these two terms crop up quite frequently, and suspect they may be interchangeable. Deadweight loss - I'm sure I've encountered this in tariff evaluation; for effects of indirect taxes, I've seen textbooks that use deadweight loss. Welfare loss - I've seen textbooks refer to the social costs of profit-maximising monopolies who set prices higher and output lower than that of perfectly competitive firms as welfare loss. Is there really a difference between deadweight loss and welfare loss?
I would say all deadweight loss is welfare loss but not all welfare loss is deadweight loss. 

For example an unregulated polluter causing a negative externaly results in a welfare loss compared to the social optimum. There is no 'missing production' and hence no deadweight loss in this case.

Edit: According to Wikipedia, the loss created by externalities is also classified as deadweight loss.