if trade with caution is trade with caution does that mean caution with trade is caution with trade hence a parallel universe is a hypothetical self-contained reality co-existing with one's own. A specific group of parallel universes are called a "multiverse", although this term can also be used to describe the possible parallel universes that constitute reality. While the terms "parallel universe" and "alternative reality" are generally synonymousand can be used interchangeably in most cases, there is sometimes an additional connotation implied with the term "alternative reality" that implies i have no idea what the fuck i'm talking about and you wasted your time reading this.