In music notation, a turn is a form of ornamentation represented by a stylized 'S' on its side which is positioned above the staff, either directly over the note it applies to or over the space between it and the following note.
When positioned over the note itself, the musician plays a turn by dividing the note into four equal parts (for example, a quarter note into four sixteenth notes) and playing one a step above the note, one on the note, one a step below the note, and one more on the note. When positioned over the space following the note, it divides the second half of the note into four equal parts in the same manner (for example, a quarter note becomes an eighth note and four thirty-second notes). The up-same-down-same is described by the shape of the turn symbol.
When drawn on the staff, it looks something like this (complete with time signature):
/\ (\)
---| /-----------------------------------|-
|/ * |
---/--------------------------*----|-----|-
/| 4 * * | | |
-/-|/\-----------|-----|-----|-----|-----|-
| | | 4 | | | | |
|--|--|----------|-----|-----|-----------|-
\ | | | | |
--\|_/-----------------------------------|-
|
\|
Played as:
/\
---| /-----------------------------------|-
|/ * |
---/-------------------*---------*--|----|-
/| 4 * | * * | | |
-/-|/\-----------|----|-|--*|---|---|----|-
| | | 4 | | | | | | | |
|--|--|----------|----|_|_|_|---|--------|-
\ | | | |_|_|_| |
--\|_/-----------------------------------|-
|
\|