In Japanese, atsui means thick whereas atsumi means thickness.
The opposite of thin (usui).
The Go Players Almanac definition:
Thick, powerful, strong. Used in the following contexts: 1. Stones with a powerful shape 2. Having superior outward influence 3. Having a safe lead in territory
John F. If you are going to talk about thickness on the basis of the Japanese terminology, you need to widen the area of discussion. There is atsusa (the word Cho is referring to in other pages here in a way that seems to surprise some people and wrongly expressed as thick territory), and a small host of phrases, each with a different and often important nuance.
The following is more or less a translation from Atsuku Utsu, one of the books kokiri needs to buy to see that Japanese texts can be much better than ours. For convenience I have created the new words MI-thickness (atsumi), SA-thickness (atsusa), ER-thickness (atsui keisei = thickER prospects) and STYLE-thickness.
QUOTE When people say "thick" (atsui) what we usually imagine is "thick shape" (atsui katachi). But you need to be aware that "thick game" (atsui go) and "thick prospects" (atsui keisei) also exist. Let us begin by distinguishing them.
"Thick shape" (atsui katachi) is also called "mi-thickness" (atsumi). The conditions for mi-thickness are that it is unaffected even if the opponent approaches it. Stones that merely face the centre have influence (seiryoku) but they do not have mi-thickness.
This "thick shape" is in almost every case obtained in compensation for giving the opponent profit. Consequently, it is clear that at some point you need to convert it into profit, since the final result of a game is determined by the size of territories.
This means, if possible, converting it into territory at an early stage by using mi-thickness for moyos or for attack. But there is a proverb that tells you not to approach thickness and so it is not easy to find the opportunities in the opening.
You will therefore turn mi-thickness into sa-thickness (atsusa) and bring about a "thick(er) game" (atsui go). If you can get a thick(er) game, it is easy to maintain the initiative in a position, and you can also take decisive action by aiming at profitable trades.
In a "thick game" there is a margin in the power relations on the board. Even without walking a tight rope you can bring about "thick(er) prospects" (atsui keisei). If, everywhere, you appear to have slightly the better of it, you have "thick(er) prospects" and the various extra profits associated with sa-thickness will manifest themselves ultimately as profitable "thick prospects".
With thick shapes, thick go and thick prospects it is often the case that ko becomes a powerful weapon, of course. Even without actually starting a ko, the mere possibility that you can may force the opponent to back down. It is a fundamental essence of a position that there are few ko threats against sa-thickness, whereas there are many ko threats against "thinness".
The features of sa-thickness vary according to the opening, middle game and endgame. But basically what lies behind it is a "thick style" (atsui uchikata). UNQUOTE
This is only a glimpse from a rather large and dense book, but it may convey the need for caution and discrimination. Not mentioned here is a big section on atsui gokei, and also an important section on STYLE-thickness based on Ishida's "100 kinds of thickness" in which the different ways top players use thickness are pinpointed (the book only gives about six - the original 100 is in old issues of Kido).
Bob Myers: Two questions. First, where does the word te-atsui fit into the above taxonomy of types of thickness, if at all, or is it purely a tactical concept? Second, what do you think of using the English word solid for one of the types of thickness, MI-thickness I would presume?
John F. I have long felt that there should be some subtle nuance to te- but I have never found it. One dictionary entry begins "Atsui: Atsui or teatsui is used in various ways, but the following three are the usual ones...." It is certainly not limited to tactical ideas as it can be used e.g. in the phrase "make the right side teatsui." And there are a few other adjectives that admit of the same reinforcing te-. Maybe it's just a way of stressing the thick as opposed to the hot meaning. I'd say it's a little like the way we may say neutrally "This is a good move" or with emphasis "this is eh good move".
As to "solid", I already said on another page that this is probably a better term but has been preempted by its use for honte and all the other accumulations of history. It would be good to be able to start afresh, but my experience is that there is too much resistance.