I'm beginning to think that in this diverse group we have different definitions for our terms.

Song/Singers circles:

Someone correct me if I'm wrong but I believe that for the most part singing circles in Ireland are places for singers to take turns 'performing'. My personal experience with song circles (Toronto) is that everyone praticipates in almost every song and we take turns leading. To that end people tend to pick songs with choruses. (Usually they sing the verse alone but participation is the focus.)

Jam Session:

In my experience this has usually been blues. Everyone plays unless they are really lost. Play backup unless it is your turn to solo. Everyone gets the opportunity to solo or pass. There is seldom a 'circle' component to this. The group somehow decides to play a particular number and away it goes.

Performance Circle:

Everyone gets taken in turn. When it is not your turn you listen unless you are invited to participate.

I have stated what I believe to be the different understanding of Song/Singer Circles. Are there other definitions of any of these categories? Are there other categories? (For example,should open mic be included?)