The tradition symbolises dread. The town doesn't want the day to come where they have to practice their tradition.
The story uses imagery when describing the rock they had selected, "...seclecting the smoothest, roundest stone"
Why are we doing this??
"This isn't fair! This isn't right!"
Repitition is used when the townspeople repeat the name Dunbar, "Dunbar, several people have said, Dunbar, Dunbar"
The tone for the town is suspense. It's suspense because the townspeople don't know who is going to be picked next as the "winner" of the lottery.
The theme of this story is that traditions are not always needed. I know this because the lottery is a tradition that the townspeople do but it's not a good one, many begin to question whether or not they are doing the right thing.