Portfolio

A portfolio is the full collection of investments an individual or institution holds, considered together rather than position by position. Portfolio-level thinking is the basis of modern risk management: a single stock's volatility matters less than how that stock behaves relative to everything else you hold.

Two positions that each look risky in isolation can combine into a less risky portfolio if they tend to move in opposite directions, which is the core insight behind diversification and why professional risk analysis is done at the portfolio level, not the individual holding level.