immediately; at once; at that moment; at the moment
当 · 6 strokes
Phonosemantic compound. 田 represents the meaning and 尚 represents the sound. The simplified character 当 was adapted from the cursive form of the traditional character 當.
下 · 3 strokes
Originally a small line or dot below a longer line, indicating "down". The vertical line was added to distinguish the character from 二 (two). Opposite of 上.