The big seal script of character Deficiency or Deficit is
Which is very similar to character At (Post 488), except the middle vertical line doesn't go through to the top short horizontal line. It means that the player doesn't have enough air flow to make the instrument to produce sound: the deficiency of the air flow.
In comparison with character 乎(Post 489) and character 平 (Post 490), there are no dots, which are indicative of the air flow, between the two short horizontal lines.
Some people believe that the character is same as character At (Post 488), because the small seal script of character At
is so similar to big seal script.
However, the small seal script of character Deficiency or Deficit is
The left top
is the Tiger head.
The bottom
is Short Tail Bird (Post 107).
The right part is the character At, here it means Deficit. A tiger that just ate a small bird is deficit of energy.
The clerical script of the character is
Similar to small seal script.
The song typeface of the traditional character is
虧
Same as the clerical script.
The song typeface of the simplified character is
亏
Just the right of 虧.
The Pinyin of both characters is Kui1.
The simplified Chinese merged the two into 亏, eliminated 虧. But both existed in shell bone script.