From 8-dancer formations consisting of 4 inside dancers and 4 outside dancers.
The inside 4 dancers do the given call working within the Center of the set as
  the outside 4 dancers do the given call working with each other,
  around the outside of the set.
Notes:
- 
A good way to think about Concentric is to imagine dropping a
    stone in a pool of still water and watching the concentric rings
    rippling outward from the center where the stone dropped.  If you
    overlay that image in your mind on top of the square, the Center 4
    dancers would be working within the innermost ring, and the Outside
    4 dancers would be working between the innermost ring and the next
    outside ring.  Each group of 4 works independently of the other group
    of 4, maintaining their respective relationship from the other group
    and the very center of the set.
- 
The inside 4 dancers always do the call normally working in the Center.
- 
The ending positions for the outside 4 dancers depends upon
    the kind of formation (explained below).
| (A) | If the given call ends in a 1x4, a Diamond, or a Single 1/4 Tag,
  then there is only one possible ending formation: a 1x4 is split in half,
  and distributed as two 1x2 formations on opposite sides of the inside
  dancers; a Diamond or Single 1/4 Tag is split into 4
  pieces, and distributed like the points of a Galaxy. | 
| The above formations show the ending positions for the
  outside dancers when the given call ends in a 1x4 or
  a Diamond.  The dashed boxes represent the Center 4
  dancers who could be in a 2x2 (as shown), a 1x4
  (horizontal or vertical), or any other 4-dancer formation. | 
| |   |  |   |  | before Outsides Concentric Pass The Ocean
 |  | after 
 | 
 | 
| |   |  |   |  | before Outsides Concentric Switch To A Diamond
 |  | after 
 | 
 | 
| (B) | For the outside 4 dancers, if the given call starts
  and ends in a 2x2 then the following rules apply: If the outside 4 started as if they were Ends of Parallel Lines, then
    they must finish so that they are Ends of Parallel Lines.Similarly, if the outside 4 started as if they were Ends of Columns,
    then they must finish so that they are Ends of Columns.
 The two rules above are known as the 'Lines-to-Lines, Columns-to-Columns' rule.
  That is, if you start in Parallel Lines, you must end in Parallel Lines; if you start in
  Columns, you must end in Columns.  Note that the final formation
  may not actually be Lines or Columns, since the Centers may end T-Boned to the Ends. | 
| Examples of formations in which the Outside 4 dancers "think" they are Ends of Lines: 
 | 
| Examples of formations in which the Outside 4 dancers "think" they are Ends of Columns: 
 | 
Outsides Concentric Walk & Dodge:
| |   |  |   |  | before Outsides
 Concentric Walk & Dodge
 |  | after 
 | 
 | |   |  |   |  | before Outsides
 Concentric Walk & Dodge
 |  | after 
 | 
 | 
Outsides Concentric Partner Tag:
| |   |  |   |  | before Outsides
 Concentric Partner Tag
 |  | after 
 | 
 | |   |  |   |  | before Outsides
 Concentric Partner Tag
 |  | after 
 | 
 | 
| (C) | For the outside 4 dancers, if the given call does
  not start in a 2x2 but ends in a 2x2
  then the following rule applies: The Outside 4 must end in the positions so that the long axis of
    the setup changes by 90°.  Many formations in square dancing have a long axis and a short axis.  That
    is, the formation is visibly longer in one direction (long axis) than 
    the other direction (short axis).  When dancing the Concentric Concept,
    if the outside 4 do not start in a 2x2, but end in a 2x2,
    then they must end on the
    footprints which change the original long axis of the formation by 90°.
 | 
| |   |  |   |  | before Outsides
 Concentric Recycle
 |  | after 
 | 
 | |   |  |   |  | before Outsides
 Concentric Hinge
 |  | after 
 | 
 | 
| Concentric Bend The Line: 
 |   |  |  RIGHT    |  |  WRONG    |  |   |  |   |  |   |  | before Concentric Bend The Line
 |  | after |  | This ending formation is incorrect since the long-axis did not change
 | 
 | 
| 
 |   |  |  RIGHT    |  |  WRONG    |  |   |  |   |  |   |  | before Concentric Turn & Deal
 |  | after |  | This ending formation is incorrect since the long-axis did not change
 | 
 | 
| 
 |   |  |  RIGHT    |  |  WRONG    |  |   |  |   |  |   |  | before Concentric Linear Cycle
 |  | after |  | Ending here feels 'right' but is incorrect since the
 long-axis did not change
 | 
 | 
Concentric Touch 1/4: (using the Lines-to-Lines, Columns-to-Columns rule)
| |   |  |   |  | before Concentric Touch 1/4
 |  | after 
 | 
 | |   |  |   |  | before Concentric Touch 1/4
 |  | after 
 | 
 | 
Concentric Chase Right: (using the Lines-to-Lines, Columns-to-Columns rule)
| |   |  |   |  | before Concentric Chase Right
 |  | after 
 | 
 | |   |  |   |  | before Concentric Chase Right
 |  | after 
 | 
 | 
More notes:
- 
As soon as you hear the word 'Concentric', check to see if you are in
    Lines or Columns.  If you are not in either Lines or Columns, check the
    orientation of your long axis.
Single Concentric Concept [C4]:
 From a 1 x 4 or other applicable 4-dancer
  formations.  Centers work with each other to do the given call as Ends work
  around the Centers to do the given call.
| |   |  |   |  | before Single Concentric
 Single Wheel
 |  | after 
 | 
 | 
 See also Cross Concentric Concept [C2].