What Is the Difference Between an Arachnid and a Spider?

Many people use the term “spider” and “arachnid” interchangeably, but do these words mean the same thing as everyone assumes? I personally have always assumed that an arachnid and a spider were one and the same thing. Actually, arachnids include a variety of different creepy crawlies that you probably had no idea were actually arachnids, but not spiders.

There are, in fact, eleven orders of arachnids. These include such bugs like scorpions, mites, ticks, harvestmen, psuedoscoprions, whipscorpions, solpugids, and last, but not least, spiders. Experts compare people's confusion between arachnids and spiders in the same way that the relation between beetles and insects is misunderstood. Many people, even some experts, don’t realize that beetles are only one order of insect, the coleoptera. And obviously not all insects are beetles, just as not all arachnids are spiders. And that is the end of that.

Are there any other types of arachnids that were not listed in the article?