They can, but they really dont like it much for some reason (too bony so uncomfortable?)
Mine usually stand or lie down
Before I had Islay and Flick I did think that greyhounds never barked - none of mine ever made a sound - but sadly these two have proved that theory very wrong
LOL - I thought that too Lou, mine were quite sedate and serious so didnt wag much. The black-and-white-greyhound show wag their tails all the time though - sooooo cute
Mine can "sit" on command but rarely does it unless he thinks there's something in it for him.
When he does, though, he actually rests on his hocks and his bottom is still inches off the ground so it's not comfortable at all and he slides on slippery surfaces because he has to hold himself up on his front feet. So no, technically he can't sit like other types of dogs do.
He does bark but not much and usually only a little when he's playing. He did get woken up in the night once and barked in a truly threatening manner, which was comforting.
It took him ages to get enough control of his tail to wag it. When he was young it literally touched the ground if he was tired but luckily it stayed the same length as he got taller. For awhile it would wag sometimes but he seemed to have no control over it but now he's got a handle on it. I have to say, though, he doesn't wag it randomly and only slowly if he's really excited.
When he was a puppy he couldn't reach anything he held in his paws, which made bones etc a real trick and he had to hold them by crossing his legs. Luckily his nose grew
Bes (technically I'm told she's a lurcher but very greyhound like) finds it quite difficult to sit. She does it when asked but i don't think i have ever actually seen her choosing to do it (unless she thinks she's getting a treat!). her bum wavers about an inch or so of the floor so all her weight is on her legs.