外差

• 夕(evening; crescent moon (pictographic))RADICAL
• 卜(divination; fortune-telling)PHONETIC

Evening outside divining fortunes under the moon — that's an external affair.

• 羊(goat)ASSOCIATIVE
• 工(craftsman; work)PHONETIC

Each hair of a goat differs from the rest, just like differences that are uneven and varied.