• 鳥(bird (pictographic))

The character depicts a bird with an eye, body, wings, and four flame-like dots representing its feathered tail.

• 酉(wine vessel; ferment)
• 夋(slow manner; leisurely pace)

Fermenting alcohol produces sourness, which is exactly the character for sour.

• 二(number two; two horizontal strokes)

Two parallel horizontal strokes symbolize the number two.

• 鳥(bird (pictographic))

The character depicts a bird with an eye, body, wings, and four flame-like dots representing its feathered tail.

• 酉(wine vessel; ferment)
• 夋(slow manner; leisurely pace)

Fermenting alcohol produces sourness, which is exactly the character for sour.

• 二(number two; two horizontal strokes)

Two parallel horizontal strokes symbolize the number two.