mobility difference
A relative measure of how freely one group or side can develop compared with another.
mobility difference is the difference in mobility between competing stones, groups, or sides. It describes whether one has more practical options for extending, connecting, escaping, attacking, or responding than the other.
Mobility is judged from the legal and strategically useful continuations available in the position. The comparison concerns those possible continuations, not merely the number of liberties. This makes mobility difference a tool for evaluating strategic flexibility and identifying which group or side can act more freely and efficiently.
Unlike a mobility count, which records an absolute number of options, mobility difference is relative. It is also broader than a simple liberty difference. Because mobility depends on context, many nominally available moves may be inefficient or lose sente; the concept is therefore not a direct measure of territory, strength, or liberties.