Pincer Nomenclature
The idea of a pincer (hasami) is to obstruct a clear two-space extension.
There are six possible pincer points against an approach.
Black makes a pincer against the marked white stone by playing next at one out of a to f.
Here a, c and e are called low pincers, because they employ the third line. And b, d and f are called high pincers.
Many considerations are involved in choosing between a high vs low pincer. Sometimes there are several equally correct choices of pincer.
In this position all six pincers are seen in professional games (though the one at c is out of fashion). The same is true when Black has the 4-4 point and White approaches (at 6-3): with all pincers correspondingly moved one to the right, of course.
When White approaches 3-4 at 5-4 some of low pincers are rare (see missing pincer). Discussion there suggests a new concept of quasi-pincer.
The close pincers are a and b. These are the most forceful. That doesn't mean that they are the best, or most common. It depends how the fighting will proceed - a closer pincer may be counter-attacked more easily by a counter-pincer[1].
The close pincers are called one-space low (high) pincers (for example the 4-4 point low approach one-space low pincer). And so on with the two-space and three-space pincers, the number referring to the gap (the number of clear lines).
For many years the two-space high pincer (in Japanese, nikentakabasami) was the favoured pincer of professionals in the position shown; but that judgement no longer has the same standing.
A four-space pincer would be a pseudo-pincer.
[1]
There are two distinct usages for 'counter-pincer'.
Here is called a counter-pincer, looking at its effect on
.
Here is called a counter-pincer, for its effect on
.