What is product-market fit?

Product-market fit is the point at which a product satisfies real market demand strongly enough that growth starts to pull rather than push: users stick, referrals happen, and sales conversations shift from “why would I need this” to “how fast can I start.” Marc Andreessen popularized the term; the common proxy measures are retention curves that flatten and Sean Ellis’s “very disappointed” survey threshold.

Fit is relative to alternatives, not absolute: a product has fit until something meaningfully better arrives for the same job. That is why post-PMF companies keep watching the market — fit can be lost to a competitor’s launch as easily as it was won.