Imagining

To form a mental image of something; to envision or create something in one's mind.

"Try to imagine a pink elephant."

To believe in something created by one's own mind.

"She imagined that the man wanted to kill her."

To assume

"I imagine that he will need to rest after such a long flight."

To conjecture or guess

"I cannot even imagine what you are up to!"

Something imagined; a figment of the imagination.