Product-market fit is the point at which a product satisfies real market demand well enough that customers are pulling it forward, through organic growth, low churn, and strong word of mouth, rather than the company having to push it out through effort alone.
There's no single universal metric that proves product-market fit exists, but common signals include retention curves that flatten out instead of continuing to decline, inbound demand that outpaces what marketing spend alone would produce, and customers who'd be genuinely disappointed if the product disappeared.
A company without product-market fit yet is usually better off spending on learning and iterating than on scaling distribution, since paid growth applied to a product people don't actually want just accelerates how fast the company burns through its runway without fixing the underlying problem.
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