Both envision and envisage mean to visualize, but they differ slightly in connotation. To envisage is to contemplate or consider something—usually something real—in a certain way, or to predict a particular set of circumstances based on evidence or strong belief. Envisaging often relates to planning real-world projects. When you envision something, it’s usually more hypothetical, imaginary, or removed from reality.
The difference is subtle, but think of it this way: Envisaging usually involves something real, while envisioning involves mostly imaginary elements. You might envision a distant goal that you have not begun to work toward. Later, as you plan how to reach that goal, you might envisage how you’re going to do it with the time and resources you have available.
In these examples, envisaging involves imagining or planning tangible realities:
He said he did not envisage delivery days being cut even further if the legal challenge regarding LVCR failed. [BBC News]
His iconic landscapes envisage humans as part of an organic whole. [NY Times]
We envisage that work will take approximately six weeks to complete. [Worcester News]
And in these examples, what is envisioned is further removed from reality:
The latest plans for downtown Dallas envision a series of urban subway stations. [NBC DFW]
And envision this against the magnificent backdrop of the New York City skyline. [Broadway World]
I envision a Howard Hawks-style screwball comedy about two directors at the same awards ceremony. [Eye Weekly]