差

The 工 radical at the bottom serves as the indexing handle and represents a measuring tool — a carpenter's square. Combined with the sheep above, the character pictures the act of measuring and grading livestock. The discrepancies revealed by such measuring became the abstract 'difference, lack.' Indexing radical.

The upper portion is a compressed 羊 (sheep) — head and horns visible. Combined with the 工 (work/tool) component below, the original character depicted measuring or selecting sheep, comparing one to another. From 'comparing/sorting' came 'difference,' and from notice of inequality came 'poor, lacking.'