不是…吗【búshì … ma】

不是…吗 wraps a statement the speaker takes to be true. It reminds the listener of it, often because what is happening now doesn't fit.

The expected answer is yes. The tone ranges from a mild reminder to surprise to reproach, depending on what comes next.

When the thing has already happened, 了 goes before 吗.

不是 can sit in front of the subject

Put 不是 at the start when the point of the question is who or what.

Always 不是

This frame is built on 是, and 是 is negated with 不 in every time frame. Even about the past, 没 doesn't replace it.

• × 你没是说过吗？ → 你不是说过吗？