What is…

Customer Acquisition Cost (CAC) is total sales + marketing spend divided by new customers acquired in that period.

Product-Market Fit (PMF): you have it when ≥40% of users say they would be "very disappointed" if your product disappeared (Sean Ellis test, 2009).

MRR is the predictable monthly revenue from active subscriptions, normalized to a monthly basis.

ARR is the annualized value of all active subscription contracts at a point in time. Simply: MRR × 12.

LTV (Lifetime Value, sometimes CLV) is the total profit one customer generates over their entire relationship with you.

Churn rate is the % of customers (or revenue) you LOSE in a given period. Customer churn = customers lost / customers at period start.

NPS is a single-question survey measuring customer loyalty: "On a 0-10 scale, how likely are you to recommend us to a friend?" Promoters…

Gross margin is revenue minus cost of goods sold (COGS), expressed as a percentage of revenue.

Burn rate is how fast a company spends cash, usually measured per month. Gross burn is total monthly cash out; net burn is cash out minus cash in.

Runway is how many months a company can keep operating before it runs out of cash: current cash ÷ net monthly burn.

Net margin (net profit margin) is net profit divided by revenue, as a percentage — what remains after ALL costs: COGS, operating expenses, interest, and tax.

Contribution margin is revenue minus all VARIABLE costs — the amount each sale "contributes" toward covering fixed costs and then profit.

Conversion rate is the percentage of people who take a desired action out of those who had the chance to. Formula: (conversions ÷ total visitors) × 100.

ARPU (Average Revenue Per User) is total revenue divided by number of users over a period. Formula: revenue ÷ active users.

Burn multiple is net cash burned divided by net new ARR added in a period — how much you spend to add one dollar of recurring revenue.

Value-based pricing sets the price according to the value a product creates for the customer — what they are willing to pay — rather than its cost…

Price anchoring is a cognitive bias where the first price you see (the anchor) shapes how you judge every later price.

The decoy effect (asymmetric dominance) is when adding a third, deliberately inferior option makes one of the original two look more attractive…

The Eisenhower Matrix is a 2×2 grid that sorts tasks by urgency and importance into four quadrants — Do (urgent + important), Schedule (important, not urgent)…

Time blocking is scheduling your day into dedicated blocks, each assigned to a specific task or type of work, instead of working from an open to-do list.

The Pareto principle — the 80/20 rule — observes that roughly 80% of results come from about 20% of causes.

A sales-qualified lead (SQL) is a prospect that marketing has vetted and sales has accepted as worth pursuing — one who has shown enough fit and intent…

A sales pipeline is the stage-by-stage view of every open deal — from first contact through to close.

Sales velocity measures how fast revenue moves through your pipeline.

Compound interest is interest earned on both the principal AND previously-earned interest. Formula: A = P(1 + r/n)^(nt).

Inflation is the rate at which prices rise over time, reducing purchasing power. Measured via CPI (Consumer Price Index) in the US.

An ETF (Exchange-Traded Fund) is a basket of securities — stocks, bonds, commodities, or a mix — that trades on a stock exchange like a single stock.

An index fund is a mutual fund or ETF that passively tracks a market index (S&P 500, total stock market, etc.) instead of trying to beat it.

Dividend yield is annual dividend per share divided by stock price, expressed as a percentage.

APR (Annual Percentage Rate) is the yearly cost of borrowing as a percentage — it bundles the interest rate PLUS required fees…

APY (Annual Percentage Yield) is the yearly return on savings INCLUDING the effect of compounding — the true rate you actually earn.

Amortization is paying off a loan through fixed regular payments split between interest and principal.

Mortgage (discount) points are an upfront fee you pay the lender to lower your loan's interest rate.

A mortgage escrow account is where your lender's servicer holds money for property taxes and homeowners insurance.

A zero-based budget gives every dollar of take-home income a specific job — spending, saving, or debt — until income minus all assignments equals zero.

A sinking fund is money set aside a little at a time toward a specific, known, future expense — so the cost is pre-funded instead of arriving as a shock.

Your savings rate is the share of take-home income you save: savings divided by take-home pay.

Your debt-to-income (DTI) ratio is your total monthly debt payments divided by your gross monthly income, as a percentage.

Net worth is everything you own (assets) minus everything you owe (liabilities) at a single point in time.

The debt snowball pays minimums on every debt and puts all extra money toward the smallest balance first; each payoff rolls its payment into the next debt.

Dollar-cost averaging invests a fixed amount at regular intervals rather than all at once, buying more shares when prices are low and fewer when high.

Deep Work (Cal Newport, 2016): "Professional activities performed in a state of distraction-free concentration that push your cognitive capabilities to their…

Flow is a mental state of complete absorption in an activity, identified by psychologist Mihaly Csikszentmihalyi in 1975 — time distorts…

Procrastination is voluntarily delaying an intended task despite expecting to be worse off for the delay.

A growth mindset is the belief that abilities can be developed through effort, strategy, and feedback — coined by psychologist Carol Dweck.

Atomic habits are small, foundational routines — the basic units of a larger system of behaviour — that compound over time.

Habit stacking is a behavior-change technique that anchors a new habit to an existing one using the formula "After [CURRENT HABIT]…

Keystone habits are routines that trigger a cascade of other positive changes.

REM (Rapid Eye Movement) sleep is the sleep stage where most vivid dreaming occurs, the brain is highly active, and the body is temporarily paralyzed (atonia).

The circadian rhythm is the body’s internal ~24-hour clock that regulates sleep, alertness, hormone release, body temperature, and metabolism.

VO2 max is the maximum rate at which your body can take in and use oxygen during intense exercise…

Progressive overload is the training principle of gradually increasing the demand placed on the body so it keeps adapting.

Umami is the fifth basic taste — the savory, meaty, deeply satisfying flavor from glutamate amino acid.

The Maillard reaction is a chemical reaction between amino acids + reducing sugars in food, accelerated by heat (250-350°F+).

Pasteurization is a heat treatment that kills pathogenic bacteria, yeasts, and molds in food + beverages while preserving flavor + texture.

Autolyse is a 20-60 minute rest of flour + water (only) before adding salt or yeast. The flour fully hydrates and enzymes break down starches.

Gluten development is the formation of an elastic protein network from wheat flour proteins (gliadin + glutenin) when mixed with water.

Cloudy brine is normally a sign the ferment is working — it is suspended lactic-acid bacteria plus starch and cellular material released by the vegetables.

The consensus pick among astronomy educators is a 6–8 inch Dobsonian reflector: the most aperture per dollar on the simplest possible mount.

Per the ASPCA's toxic-plant database: spider plants, Boston ferns, areca and parlor palms, calathea, peperomia, African violets…