Product-Market Fit
When a product satisfies a real need in a specific market and customers keep using it persistently. The term was popularized by Marc Andreessen.
Growth ConceptsTerm 21 / 81
In practice
There is no single number, but the signs are readable: strong retention, unprompted word of mouth, and customers who would genuinely mind if the product disappeared. Scaling before fit is pouring water into a leaky bucket.