Hard to define, even harder to find. Exploring your customer retention, defined by product and marketing data, through the lens of meaningful business metrics and the sophisticated, agile use of experimentation is one way to design the path towards Product-Market Fit.
A Working Definition
A great definition, put forward by legendary investor Marc Andreesson, is that you have Product-Market Fit when you are in a great market, with a product that can satisfy that market.
Signs of Product-Market Fit
Indications of Product-Market Fit include the marked reduction of churn and a stable level of n-day retention metrics that no longer trend towards zero.
How to Find Product-Market Fit
The path towards Product-Market Fit includes primary customer research, ideally of behavioural observation, that clearly articulates an unmet need, for a market that is of sufficient size and revenue potential to make a successful business.