Uchi-soto in the Japanese language is the distinction between in-groups (uchi, 内, "inside") and out-groups (soto, 外, "outside"). This distinction between groups is not merely a fundamental part of Japanese social custom, but is also directly reflected in the Japanese language itself. One of the complexities of the uchi-soto relationship lies in the fact that groups are not static; they may overlap and change over time and according to situation.