Fantasise is a term that can be used to describe the act of daydreaming, dreaming, imagining, and conceiving. Daydreaming is the act of allowing one's mind to wander and become lost in thought. Dreaming is the act of having a series of thoughts, images, and sensations that occur in the mind during sleep. Imagining is the act of forming mental images or concepts of what is not actually present. Lastly, conceiving is the act of forming an idea or plan in the mind. All of these activities are related to fantasising, which is the act of indulging in imaginative daydreams or fantasies.