Crochet is a process of creating fabric from yarn or thread using a crochet hook. The word is derived from the Middle French word croc or croche, meaning hook. Crocheting, similar to knitting, consists of pulling loops of yarn through other loops. Crochet differs from knitting in that only one loop is active at one time (the sole exception being Tunisian crochet), and that a crochet hook is used instead of knitting needles.
Crocheted fabric is begun by placing a slip-knot loop on the hook, pulling another loop through the first loop, and repeating this process to create a chain of a suitable length. The chain is either turned and worked in rows, or joined to the beginning of the row with a slip stitch and worked in rounds. Rounds can also be created by working many stitches into a single loop. Stitches are made by pulling one or more loops through each loop of the chain. At any one time at the end of a stitch, there is only one loop left on the hook. Tunisian crochet, however, draws all of the loops for an entire row onto a long hook before working them off one at a time.
Typical materials for crochet hooks wood, plastic, casein, or aluminum. Historical examples also include bone, steel, porcupine quill, celluloid, agate, ivory, and fossilized mammoth ivory. They can have decorative handles. The handle may be shaped to fit the hand for easier use. Some hooks are made with wooden or plastic handles with the hook made of metal and inserted into the handle.
An alternative form is the Tunisian crochet hook, which is much longer than a regular crochet hook, in order to accommodate the multiple loops used in Tunisian crochet. A type of crochet needle with a hook at each end, known as a cro-hook, is used to make double-sided crochet pieces.