That applies to crochet as well. Just when you thought it was safe to assume that the (US) name of a stitch told you how many loops to have on your hook when you begin, and how many pairs of loops to remove... along come half stitches.
The most common half stitch is half-double crochet, so let's go over it step by step.
Like regular double crochet, half-double crochet (hdc) starts with two loops on the hook. We create that second loop with a yarn over.
So it starts out like a double crochet and ends like a single crochet.
To work half-triples (or taller) then, you would work the stitch as named until you have three loops remaining on your hook. (In the care of a triple, start with three loops, and remove in pairs until three loops remain.) Yarn over, and remove those last three loops together.
So with a half-double stitch you not only have back loop only (BLO) and front loop only (FLO) but third loop only.
Just like all the other stitches, half double crochet can also be increased, decreased, posted... here let me show you.