Every FIRE term, explained — with a real number from the model

How your portfolio is split across asset classes — equities, bonds, cash, property and more — which drives both its expected return and its volatility.

Leaving full-time work for part-time or lower-stress work that covers part of your spending, so your portfolio only has to fund the rest.

The stretch between retiring and your pensions or state benefits starting, which your portfolio alone must fund.

Splitting a retirement portfolio into short-, medium- and long-term "buckets" (cash, bonds, equities) so near-term spending is insulated from a market downturn.

The point at which your existing savings, left to grow untouched, will reach your FIRE number by your target retirement age — so you can stop investing new money and just cover living costs.

A withdrawal strategy that spends your portfolio down to (near) nothing by the end of your life expectancy, rather than preserving it indefinitely at a fixed safe withdrawal rate.

Ember's single composite score for plan health, blending progress to your FIRE number with resilience factors like diversification and debt.

The annual percentage a fund charges to manage your money, deducted from returns before you ever see them.

Reaching financial independence at a comfortably high spending level, which requires a correspondingly larger portfolio.

Having enough invested wealth that paid work becomes optional — the "FI" in FIRE.

The portfolio size that lets you sustain your planned spending for the rest of your life without paid work.

Retiring to — or spending time in — a lower-cost country so the same lifestyle needs a smaller portfolio.

A pre-planned, gradual shift in asset allocation over time — typically from growth assets toward capital preservation as retirement approaches.

Replaying your plan against one specific real historical sequence of returns — e.g. retiring at the start of 1929 — instead of a randomly sampled one.

Outside the US, the HSA's tax-advantaged medical saving has no direct match — most FIRE-ers instead budget a standalone private health-insurance buffer for the years before state healthcare eligibility.

Prices rising over time erodes what a fixed amount of money can buy — modelling "in real terms" strips that erosion out so figures stay comparable across decades.

Reaching financial independence on a deliberately minimal annual spend, which produces a smaller required pot than a typical FIRE target.

Running your plan through thousands of randomly sampled market-return sequences to see what share of them leave your portfolio intact.

A nominal return is the raw percentage a portfolio grows by; a real return subtracts inflation, which is what actually protects your future spending power.

Periodically buying or selling to bring a portfolio back to its target asset allocation after markets move it off-target.

The US forces Required Minimum Distributions from tax-deferred accounts from a set age; most other countries instead cap how much of a pension can be taken as a tax-free lump sum, with no forced annual draw.

The Roth IRA's closest UK/EU counterpart is a stocks-and-shares ISA-style wrapper: contributions are taxed going in, growth and withdrawals are tax-free.

A safe withdrawal rate is sized to last your life expectancy; a perpetual ("never touch principal") rate is sized to last forever, which needs a smaller draw or a larger pot.

The percentage of your portfolio you draw each year in retirement — the classic 4% rule, though early retirees usually need a lower rate.

Testing how much your FIRE date or required pot moves when one assumption — return, inflation, spend — changes, to see which inputs matter most.

The danger that a run of bad market years early in retirement can deplete a portfolio even when its long-run average return looks fine.

US Social Security's counterpart abroad is each country's own state pension or national retirement scheme, each with its own claim age, deferral and early-claim rules.

The observed pattern where retirees spend more in the active early years, less in a quieter middle stretch, then more again late in life on healthcare — a smile-shaped curve rather than flat spending.

A withdrawal level a portfolio can support without running out before the end of your life expectancy, whichever withdrawal basis you use to get there.

The gap between the gross amount you must withdraw from a taxable account and the net amount you actually get to spend, once income tax on the drawdown is paid.

The 1998 research (updated many times since) that tested fixed withdrawal rates against 1926–1995 US market data and is the origin of the 4% rule.

Your safe withdrawal rate is not the same as your expected investment return — a portfolio can average 7% growth and still fail at a 5% withdrawal rate once volatility and sequence risk are in the mix.

The state of having enough resources that you could stop working and still cover your spending — used interchangeably with financial independence.

The mirror image of a 4% safe withdrawal rate: your FIRE number is roughly 25 times your annual spend (1 ÷ 0.04 = 25).

The 401(k)'s closest UK counterpart is a workplace pension or SIPP: contributions get tax relief going in, and withdrawals are taxed as income later.