Aizuchi (相槌 or あいづち) is the Japanese term for frequent interjections during a conversation that indicate the listener is paying attention and understanding the speaker. Aizuchi constantly reassure the speaker 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" (that's how it is, I think)
• "sō desu ka" (is that so?)
• "hontō" or "hontō ni" (truly)
• nodding

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.

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.