Unpacking PMF definitions & terminology
Let's play a game of startup terminology bingo. Whether you're new to the startup world and overwhelmed by all the jargon and insider terminology OR you've been around the block, you know the terms are valuable.
So, we pulled the data on the top 10 product market fit terms used on top social media platforms and in newsletters right now. We know that being a human founder sponge is a challenge and it is easy to get lost in the language, so we’ve created a Terminology 101 for easy adoption as you are constantly trying to take advice for evolving strategies.
*a note before jumping in; “In theory there is no difference between theory and practice. In practice there is.” Thank you Yogi Berra, yes this applies here too– knowing all the quote-unquote Insider terms should come with concrete strategy and work!.
**yes, we know, there’s 11, we threw in the last one for good measure + it is important for first time founders (who may be living at home)
Terminology 101:
Retention Curve
A graph that shows how many users continue using your product over time. A flattening retention curve = good sign of PMF.
Activation
The moment a user first experiences real value from your product (e.g. completing a key action or reaching an “aha moment”).
Churn
The percentage of users or customers who stop using your product. High churn usually means PMF hasn’t been reached.
Net Promoter Score (NPS)
A measure of user satisfaction and loyalty—asks users how likely they are to recommend your product to others.
“Hair on Fire” Problem
A problem so urgent and painful that users are actively searching for a solution. Great PMF often starts here.
Engagement
How frequently and deeply users interact with your product. High engagement suggests the product is delivering real value.
Customer Feedback Loop
A cycle of gathering user input, iterating based on it, and testing improvements—core to reaching PMF.
Stickiness
How often users return or stay engaged. Sticky products indicate deeper value and closer proximity to PMF.
"Very Disappointed" Test
Popularized by Sean Ellis: ask users, “How would you feel if you could no longer use this product?” If 40%+ say “very disappointed,” you’re likely at PMF.
Pull from the Market
When customers are chasing the product—not the other way around. You’re struggling to keep up with demand.
The Mom Test
A framework from Rob Fitzpatrick’s book on how to talk to customers. It teaches you to ask better, unbiased questions—because your mom (and others) will lie to protect your feelings unless you ask the right way. Essential for validating whether a problem is real.
