Welllll.....sometimes...and it depends on how you define a ball. And there are Hanks and also Skeins of yarn as well.
These two little beauties are called Skeins (rhymes with reins), some people call them Hanks...I tend to call them...um Skanks. But that's just me. I read it somewhere and I liked the sound of it and well, there you go.
Most sock yarn tends to come in Skanks, which when un-twisted, open up to a big hoop of yarn which is then put on a swift and wound into a center pull ball by hand (as Cherry did) or with a yarn winder like my Hugo.
I have the ball winder, but no swift. Hence the huge balls of snot, I mean knots, when I try to ball up a Skank. Sigh.
There are also these types of balls, which can also be called as Skeins, but I don't call them Skanks. I only call the long thingies Skanks. They usually come center pull already - which is very handy I must admit. Although I will go ahead and wind them on Hugo, cos well, I like playing with Hugo and making balls. I will definitely wind them up when using acrylic from the local craft store because it comes in very large skeins and it's easier to handle several small balls than one huge center pull skein.
See the little round thing at the top of the paper sack? Well, that's another type of ball. I'm not sure if they come center pull straight from the store or not, well, cos I never give 'em a chance... Straight to Hugo with every bit of yarn that enters the Chaos!!!! I grab the first free end and start cranking.
Then there's the good 'ol standby the pure and simple ball. All rolled up, nice and purty and waiting for a Kitty to come play. Nothing wrong with a good 'ol fashioned ball, but they do tend to roll around a lot and get pounced on by Kitties, cos well, if it's rolling around and it's on the floor, it's fair game!
I prefer to wind up all my Skanks, balls and whatnots on Hugo into center pull "yarn cakes" (you can see an orange one in the photo of Hugo above). They sit nice and flat on the bottom of your project bag and just stay calm and non-rollie and then poof! they're all used up.
I hoped this answered your question J.
And now finally, off to bed. This was a wonderful distraction (thanks J!) and my decaf Yorkshire tea is all gone. Time for beddy-bye and sweet dreams.