Aizuchi [eye-zoo-chee] is the Japanese term for frequent interjections during a conversation that indicate the listener is paying attention and understanding the speaker. In linguistic terms, these are a form of phatic expression (one whose only function is to perform a social task, as opposed to conveying information).
Aizuchi are considered reassuring to the speaker, indicating that the listener is active and involved in the discussion. Aizuchi are frequently misinterpreted by non-native speakers as agreement on the part of the listener, because common aizuchi include: ‘hai,’ ‘ee,’, or ‘un’ (‘yes,’ with varying degrees of formality); ‘sō desu ne’ (‘I see’); ‘sō desu ka’ (‘is that so?’); ‘honma’ (‘really’); ‘naruhodo’ (‘I see, that’s right’); and nodding. These can be compared to English ‘yeah, yeah,’ ‘yeah, ok,’ ‘got it,’ ‘yep,’ ‘uhuh,’ or ‘go on,’ but are more pronounced and important in Japanese.
Business relations in particular can be hampered by non-native speakers assuming that their Japanese counterparts have been agreeing to their suggestions all along, when in reality the Japanese have only been saying that they understand the suggestions – ‘got it,’ not ‘agreed.’
Aizuchi can also take the form of so-called ‘echo questions,’ which consist of a noun plus ‘desu ka.’ After Speaker A asks a question, Speaker B may repeat a key noun followed by ‘desu ka’ to confirm what Speaker A was talking about or simply to keep communication open while Speaker B thinks of an answer. A rough English analog would be: ‘…you say?’ (for example upon hearing that a friend bought a new car one might reply: ‘A car, you say?’).