About 忙 and 忘 using same radicals but having different meanings


Today I confused 忙 with 忘 and now I can see why: they are made of same
radicals and yet they have different meanings. Is there a logical reason for
this?




The meanings are a bit related: when one is in _haste_ , one tends to _forget_
things.

But as for why the characters developed the way they did, you'll have to ask
someone with background knowledge of the Chinese characters themselves.

I do see that the reconstructed Old Chinese readings and researched Middle
Chinese readings aren't very far apart between the two characters:

  * 忙: " _flurried, hurried, in haste; to hasten, to hurry_ "  
Old Chinese reading: `/*mˁaŋ/`  
Middle Chinese reading: `mang`

  * 忘: " _to forget, to overlook_ "  
Old Chinese reading: `/*maŋ/`, `/*maŋs/`  
Middle Chinese reading: `mjang`, `mjang``H`

The similar semantics and similar phonetics could suggest a common root.

