Uchi-soto is a term in the Japanese language used to refer to the distinction between in-groups (uchi, "inside") and out-groups (soto, "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.

The basic concept revolves around dividing people into in-groups and out-groups. When speaking with someone from an out-group, the out-group must be honored, and the in-group humbled. This achieved with special features of the Japanese language, which conjugates verbs based on both tense and politeness. It may also include social concepts such as gift giving or serving. The uchi-soto relationship can lead to someone making great personal sacrifices to honor a visitor or other person in an out-group.

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.

Uchi-soto groups may be conceptualized as series of overlapping circles. One's position within the group, and relative to other groups, will depend on the context, situation and time of life. For example, a given person will usually have a family, a job, and other groups or organisations to which he or she belongs. His or her position within the various groups and in relation to other groups will change depending upon the position he or she is occupying at a given moment.

Thus, a company employee may occupy a superior position within the specific company, but a humble one in relation to the company's customers. The same employee may hold a black belt, giving him or her a superior position within his or her karate club, but may be a beginner at tennis and thus occupy an inferior position in the tennis club, and so on.

The workplace is a typical example: the employees below a middle manager are in his or her in-group, and may be spoken to using casual speech , while his or her bosses, or even, in large companies, people in other departments, are in an out-group, and must be spoken to politely. However, when dealing with someone from another company, one's own entire company is the in-group, and the other company the out-group. Thus, it is acceptable for the middle manager to speak of his or her own company, even the bosses, in non-honorific speech. This emphasizes that the company is one group, and although that group may have subdivisions inside of itself, it does not include the other company.

For example, when speaking with her subordinates a manager might omit the honorific -san, whereas she would be unlikely to do so when addressing her superiors. On the other hand, when dealing with an outsider -- essentially any person not directly connected to the company -- she would omit all honorifics when speaking about anyone in the company, including her superiors.

However, if the same manager speaks to a subordinate about his family, she will refer to the subordinate's family, which is his in-group but not hers, in polite terms, but her own family, which is her in-group but not his, in plain language. Thus, the manager and the subordinate would both refer to their own families as kazoku (family) and to the other's family as go-kazoku (honorable family).

Likewise, in a Japanese home the most senior family member, usually the father or grandfather, normally takes a bath first; the rest of the family follows in order of seniority. A visitor to the home, however, would be offered the first bath. Similarly, an overnight guest would be offered the best sleeping arrangements, even if this would greatly inconvenience the rest of the family.

Language examples

For detailed information, see Japanese honorifics.

Japanese honorific language ("keigo") is divided into three forms: polite, humble and respectful. Within these forms, there are specific words and prefixes.

For example, the verb "to eat" may be given as

• taberu (polite: "I/we/you/they eat" or "he/she/it eats")
• itadaku (humble, literally "to receive", used to refer to oneself or one's in-group), or
• meshiagaru (respectful, used to refer to one's superior)

and the noun "a drink" may be given as

• nomimono (one's own drink), or
• o-nomimono (someone else's drink)

Nouns involving the family, the household, or familial relations normally take honorific prefixes when denoting an out-group and not when denoting an in-group.

Some nouns change completely for the same reasons, such as chichi ("my father") versus o-tō-san ("your father") or haha ("my mother") versus o-kā-san ("your mother").