This page (still to be further updated) present stitches that are variations on basic stitches.
There is no standard terminology in Tunisian crochet, apart from basic elements. The classification below is my own personal structure. It does not come from anything official. It is not prescriptive. On internet and in books you will come across different names. In my effort to be as clear and pragmatic as possible, I opt for descriptive names based on the few existing standard elements I could find.
Modified Tunisian stitches (also called locked stitches)
Any basic stitch is called modified when, in addition to the place where the hook is inserted to make a basic stitch, you also insert your hook into the adjacent RetP chain.
Tunisian purl stitches
Any basic stitch is called purl when you move the working yarn to the front of the work before inserting the hook into the fabric to make a stitch. You move the working yarn to the back of the work just before you make a yarn over and pull up a loop.
A very interesting stitch is the Tunisian purl reverse stitch. Have a look at the bottom of the page on purl stitches to find out what is remarkable about this specific stitch.
Extended Tunisian stitches
Any Tunisian stitch is extended when you make 1 chain before moving to the next stitch.
Since extended stitches are taller than their equivalent “basic” stitches, make sure you adapt the height of your edge stitches at the start and end of rows.
Tunisian double crochet stitches
Very similar to extended stitches (yet not exactly the same), any Tunisian basic stitch can be worked like a double crochet (US terminology) but with a major difference: all loops are kept on the hook.
Tunisian crossed stitches
The basic stitch that is most used to create crossed stitches is the Tunisian simple stitch. It is this basic stitch that I use for the samples presented in the page about crossed stitches.
Twisted (up and down) Tunisian simple stitches
The only difference between the twisted up and twisted down Tss is the direction in which you rotate the hook before the yarn over.