The word “into” is a preposition that expresses movement of something toward or into something else. I made it into work a few minutes early today. The tooth fairy tucked the tooth into her pocket before placing a $1 bill under my daughter’s pillow. “In to,” on the other hand, is the adverb “in” followed by the preposition “to.”

Use “ into” to describe where something is: going inside something else. Use “ in to” based on the verb that comes before it. It can have many meanings, but here’s a quick tip that covers some of them: if you can replace it with “in order to,” use “in to.”

In this last use, the phrasal "come in" takes on a meaning closer to "into," as in coming toward, or creating a movement toward, something. "Into" can, occasionally, also take on a phrasal construction, such as, "enter into an agreement."