I’ve been part of many conversations about cross stitch in events and in almost every conversation something simple is said that raises a question; is it embroidery floss or thread?
This appears to be the biggest misunderstanding in cross stitch, so we’re going to look into which, and why.

The Answer

You cross stitch with two strands of embroidery thread; these strands are called embroidery floss. The skein is also called embroidery floss.

Floss or Thread?

We’ll start by talking about yarn. Yarn is fibers spun together to make a tightly bound material. The way that you construct this spin is the route of the issue. Yarn can be spun two ways, S and Z.

The Z twist is used in sewing machines as the twist causes less fraying and unraveling. However, S twist is used for threads specifically meant to come apart. This is where we get down to the brass tacks of the issue.
Embroidery floss (yes, floss) is made up of 6 strands of embroidery thread. The 6 strands are spun with a z twist. These are then combined using an S twist, made to come apart. As a result, when you stitch you take out 2 stands of THREAD from the embroidery FLOSS.

You’ll notice if you look closely though that DMC strands (and Anchor) are also spun together in a Z twist. So does that mean those are still threads? No. They’re still designed to come apart, so are classed as embroidery floss.

So what should I say?

Either!
Circling back to my first sentence, in every event I’ve attended someone always says “actually its embroidery floss”. Turns out that it’s interchangeable as you stitch with embroidery floss and thread.

Embroidery floss or stranded cotton is a loosely twisted, slightly glossy 6-strand thread, usually of cotton but also manufactured in silk, linen, and rayon. Cotton floss is the standard thread for cross-stitch.