| first-class; top grade; foremost; top-notch; leading; characteristic; peculiar; unique; school (e.g. of a performance art); one flag; one banner; one streamer |
| 3rd rate |
| upper stream; upper course; upper reaches; upstream; upper classes |
| downstream; lower reaches of a river; lower classes |
| mid-stream; middle course; middle class |
| mainline; mainstream; main current (stream) |
| second-rate; inferior |
| (cultural) exchange; interchange; interaction; (inter-) mingling; (social, etc.) networking; intercourse; alternating current; AC |