Common U.S. crochet abbreviations include "ch" for chain, "sc" for single crochet, "dc" for double crochet and "tr" for treble crochet. Other common abbreviations include "dec" for decreasing the number of stitches in a row or round, and "inc" for increasing the number of stitches.
The abbreviation "sp" is for space, and the term instructs users to insert a crochet hook in the space between two stitches, rather than into the stitches themselves. U.K. crochet patterns use many of the same abbreviations, but the terms refer to different stitches. For instance, a U.K. double crochet is actually the same as a U.S. single crochet stitch.