Gauge (textile crafts)
A Gauge is the amount of stitches/rows per inch (or centimeter) of a crochet or knitted item. In both crochet and knit, this is measured by making a gauge swatch.
A gauge swatch is a small sample of the pattern, made before starting the main item to allow the knitter/crocheter to measure the gauge and ensure the project will turn out to be the desired size. They are usually made in a 4" x 4" square.
After making a gauge swatch, the crocheter/knitter will measure and compare it to the specified swatch in the pattern. Adjusting their hook/needle or tension to ensure their measurements and stitches match the one in the pattern.