Software is intangible, since it requires a tangible carrier to exist.
Without hardware, software is inert math. Not only is software intangible, it is subjective in its construction, its design, and its installation. This allows software to be variable in its appearance and function, even between pieces of software designed to perform the same tasks. Hardware is very tangible, but is still subjective in its design and, for personal computers, subjective in its installation. Since software can be changed, either by executable, or source code, to perform a different function, ownership of the individual copy is implied.