You can decrease a stitch (abbreviated dec), which is really just subtracting a stitch, in a single crochet row. You decrease stitches in single crochet in the same places that you increase stitches — at the ends of the row or somewhere in the middle:
1- Insert your hook into the next stitch.
If you're decreasing at the beginning of the row, insert your hook in the first stitch.
2- Yarn over (yo) and draw the yarn through the stitch.
You should have 2 loops remaining on your hook.
3- Insert your hook into the next stitch.
You're continuing to work single crochets normally.
You should have 3 loops on your hook.
5- Yarn over and draw the yarn through all 3 loops on your hook.
You've completed one single crochet stitch decrease.
6- Take a look at these symbols for single crochet stitch decrease.
Stitch diagrams use symbols to give you a pictorial description of the pattern design — and may or may not include written directions. These are the symbols for a single crochet decrease in crochet stitch diagrams.