When a company splits, merges, spins off a unit or pays a special dividend, the occ adjusts existing contracts so holders are neither helped nor hurt. Strikes, deliverables or contract counts change, and the symbol root usually gets a digit appended.
Adjusted lines are traps for screeners and for anyone who trades off a strike alone. Liquidity collapses, spreads widen, and the displayed premium no longer maps onto the arithmetic you are used to.
Example: XYZ at $50 does a 3-for-2 split. The $52.50 strike becomes a $35 strike and the deliverable becomes 150 shares. Your call now looks cheap at $1.20 — but it controls 150 shares, so its real cost is $180 per contract, not $120.
Related: corporate-action, deliverable, occ, option-symbol