whereat

whereat用作疑问副词作at what解。用作关系副词作at which解，whereby用作疑问副词作by what解，用作关系副词作by which解，wherefrom，wherein等词也是这样。这些词使文件有“正式”或“古雅”的韵味，在一般文字里该避免，尤其该避免把它们用作疑问副词。

注意whereat等（用作关系副词）和thereat等不同，比较下面两句：

• I did not hear the remark whereat she was annoyed.
• He made a remark, and she was annoyed thereat.