A ratio spread which is constructed by involving deltas of options such that a neutral “overall” position is created. To fine-tune a delta spread or neutralize a delta position, the delta of a long option is divided by the delta of a short option, and thus the hedge ratio is established. The combined delta of the option position will be zero, and hence, a small price change won’t have any effect.

The delta spread is often called a neutral spread. Also, it is most often a calendar spread.