G: Amigurumi (編みぐるみ, amigurumi) is essentially a Japanese compound meaning “knitted/crocheted stuffed thing.”

It comes from:

• 編み (ami) — from amu (編む), “to knit, crochet, braid, or interweave.” It refers broadly to making something by working/interlacing yarn or thread, so it isn't specifically “crochet.”
• ぐるみ (gurumi) — from ぬいぐるみ (nuigurumi), meaning “stuffed toy” or “plush toy.” Nuigurumi itself combines nui (“sewing/stitching”) with kurumi, related to wrapping/enclosing something.

So ami + gurumi → amigurumi: roughly “a stuffed object made by knitting/crocheting.”

The interesting bit is that English has largely adopted amigurumi as meaning crocheted little stuffed figures, whereas Japanese ami doesn't specify crochet; an amigurumi can technically be knitted or crocheted.

G: Yes—but the crochet distinction and the knitting distinction don't line up perfectly.

For crochet amigurumi, the important distinction you're thinking of is usually working in a continuous spiral rather than completing discrete joined rounds. You don't finish each circumference, join it, and start a clearly separate next one. You just keep crocheting around and around, so the fabric follows one continuous helical path. That's why you normally need a stitch marker to know where a nominal “round” begins.

With knitted amigurumi, knitting in the round is already naturally continuous in a closely analogous way. If you put stitches on double-pointed needles, magic loop, etc., and simply keep knitting, you're producing a helix. There isn't an inherent “end this round, join, begin the next round” operation comparable to joined-round crochet.

So the comparison is approximately:

Crochet	Knitting
Flat rows	Flat knitting
Joined rounds	No particularly close knitting equivalent
Continuous spiral	Ordinary knitting in the round

And that's where the substantive difference lies. Crochet gives you a meaningful construction choice between joined rounds and a continuous spiral; ordinary circular knitting largely starts on the spiral side of that choice.

There are knitting techniques that deliberately make individual rounds more visually discrete, and you can manipulate the round boundary, but those are additional techniques rather than the basic structure of knitting in the round.

The other big amigurumi difference survives in both crafts: you're generally making small, tightly worked, three-dimensional closed forms, increasing and decreasing stitches to sculpt the surface—sphere → head, cylinder → limb, etc. In crochet, single crochet happens to be exceptionally well suited to that because it's dense, stiff, and easy to increase/decrease almost anywhere. Knitted fabric is stretchier and behaves differently under stuffing, so knitted amigurumi can use essentially the same 3-D geometry without producing quite the same structural fabric.

So if the thing that struck you about crochet amigurumi was “wait, this isn't merely ordinary crochet arranged into a circle; the actual progression of the stitches is different,” then yes, that's real—but knitting in the round was basically already doing that progression.

G: Not quite. “Closed” is characteristic of amigurumi, but it isn't a strict requirement built into the Japanese word.

Amigurumi (編みぐるみ) essentially identifies a knitted/crocheted three-dimensional stuffed or toy-like object. The -gurumi component carries the idea of something wrapped/covered, ultimately related to nuigurumi (ぬいぐるみ, stuffed toy), but it doesn't impose a geometrical rule that the fabric must form a completely closed surface.

So you can have an amigurumi piece that is temporarily open for stuffing, permanently open in some location, assembled from flat pieces and seamed, or made by knitting/crocheting back and forth rather than spiraling. None of those automatically disqualifies it.

The useful dividing line is more like:

Amigurumi describes the kind of constructed object, not the topology or stitch path used to construct it.

That's also why knitted amigurumi fits perfectly well even though its construction may differ considerably from the stereotypical crocheted-in-a-spiral technique.

If you literally crocheted a flat decorative circle using the same tight single-crochet spiral associated with amigurumi, the technique wouldn't make the circle amigurumi. Conversely, a little stuffed animal assembled from several knitted pieces can absolutely be amigurumi.