A clean quantitative framing is this: the bid-ask spread is a market maker's compensation for providing immediacy. Three quick checks before you act: 1. Name the mechanism in plain English: Spreads are wider when uncertainty is high, when the asset is illiquid, or when the market maker suspects adverse selection. 2. Say why it matters for behavior or portfolio decisions: Understanding spread dynamics helps you time executions and choose between aggressive and patient order types. 3. Set the review question: Write down the state variable you would monitor first if this thesis started to drift. Market translation: Right before earnings, spreads on single-name options widen because the market maker is uncertain about the magnitude of the move. Failure mode: The mistake is crossing the spread aggressively on every trade without considering whether the urgency is real. That is the kind of small conceptual habit that compounds into better decisions over time.