This is another way to memorize vocabulary and not forget, especially for more visual learners. The shapes of the objects.
Putting mental or visual labels on objects according to their shape can bring a word to expression when you do not remember exactly its name but the category in which you labeled it.
Sort these objects according to their shape: la ventana, el bolígrafo, la pelota de tenis, la puerta, la Tierra, el tubo, la rueda, la lanza, el televisor.
REDONDO-A / RECTANGULAR / ALARGADO-A
ROUND-A / RECTANGULAR / ELONGATED-A