亻
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丿
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丨
:
Mnemonic symbol: Rosa Luxemburg. She's quite radical, and her name starts with "r", just like "ren2". Also, 亻appears at the left-hand side of characters, and Rosa is a leftist as well.
Robinson Crusoe (r) and Rosa Luxemburg (亻) are having their favorite snacks in the encampment's kitchen: Rosa is eating a banana (丿) and Robinson is eating a dinosaur bone (丨).
非
=
三
+
丿
+
丨
:
Mnemonic symbol: a negative film (photography).
Frankenstein's monster (f) made an effort to photograph the Eiffel Tower (ei1), but now his negative (非) is a big mess. In front of the tower he set up a camera on a Cartesian coordinate system (三) as a tripod, and he attached a banana (丿) and a dinosaur bone (丨) to the camera so that he can finely tune the angles. All was for naught as he now holds the messed up negative in his hands.