Today’s troublesome pair is perspective and prospective. Why do I think these two get mixed up? Because they are longish words that are spelled very similarly!
The main meaning of perspective is the art of representing three-dimensional reality on a two-dimensional surface to give an impression of objects’ relative distance and size (a classic example of this is painting a picture of a tiled floor; an example of using this for amusing means is found when you take a photo that you have the Pyramids in your hand, or similar) and by extension it means the appearance of objects with regard to their relative position and distance from the person viewing them. Other meanings, which you can see are linked to this idea, include a particular way of viewing things (“from the rioters’ perspective, they had every right to take the trainers”), and an understanding of the relative importance of things (“you need to keep a sense of perspective about what he has done: stealing a tube of Polos is not as bad as mass murder”).
Prospective, more simply, means likely or expected to happen or be in the future – “I’d like to welcome my prospective son-in-law into the family – he will marry my daughter in September”; “with my prospective earnings for 2012, I will be able to retire in 2050”.
“From Mrs Brown’s perspective, having a prospective neighbour who was good at picking locks was a godsend, as she was always losing her front door key.”
So the meanings should not be that easily mixed up; it just requires a moment of pause, perhaps, before writing down the particular word you choose.