Glossary
Every term the lessons use, defined in plain language. If a definition here needs its own glossary, it is a bad definition.
A
Amortization
Paying off a loan in equal instalments where each payment covers that month's interest first and whatever is left reduces the balance. Early payments are mostly interest; later ones are mostly principal.
Annual Percentage Rate (APR)
The yearly cost of borrowing including fees, not just the headline interest rate. It is the only number worth comparing between two loan offers, because a low rate with heavy fees can cost more than a higher rate with none.
Asset allocation
How a portfolio is split between types of investment, typically shares versus bonds. It drives more of the outcome than picking individual holdings does.
B
Basis point
One hundredth of a percentage point. 50 basis points is 0.5%. Used because 'half a percent' and 'a half percent increase' are ambiguous in a way that '50 bps' is not.
Bear market
A fall of 20% or more from a recent peak. The threshold is a convention rather than a law of nature, but it is the one everyone quotes.
Bond
A loan you make to a government or company. They pay you interest for a set period and return the original amount at the end. Lower expected return than shares, and usually less volatile.
C
Compound annual growth rate (CAGR)
The constant yearly rate that would turn a starting value into an ending value over a given period. It smooths out the bumps, so it describes the journey's average but not its ride.
Compound interest
Interest that earns interest. Because each period's growth is added to the balance the next period grows from, the total rises by a power rather than a multiple, which is why time matters more than the rate.
Credit score
A number summarising your borrowing history, which lenders use to price the risk of lending to you. A worse score does not usually mean refusal. It means a higher rate.
D
Diversification
Spreading money across different investments so that one going badly does not take everything with it. It reduces the range of outcomes rather than raising the average.
Dividend
A share of a company's profit paid out to shareholders, usually quarterly. Not guaranteed, since companies can cut or stop them.
Dollar-cost averaging
Investing a fixed amount on a fixed schedule regardless of price. You buy more units when prices are low and fewer when high, which removes the need to guess the right moment.
Drawdown
How far an investment has fallen from its previous peak, as a percentage. The maximum drawdown is the worst such fall over a period, and it is often a better measure of what an investment felt like to hold than its average return.
E
Effective tax rate
Total tax divided by total income, which is what you actually pay. Always lower than your marginal rate, because your first dollars are taxed in the lowest brackets.
Emergency fund
Cash set aside to cover several months of essential expenses if income stops. Kept in savings rather than investments, because its whole job is being certain in value on the day you need it.
Equity
Two meanings. In investing: ownership in a company, i.e. shares. In property: the part of a home's value you actually own, being its value minus the mortgage.
Expense ratio
The annual fee a fund charges, as a percentage of your balance. Small-sounding numbers compound: 1% a year removes roughly a quarter of your ending balance over 30 years.
I
Index fund
A fund that holds everything in a market index rather than trying to pick winners. Cheap to run, so its fees are low, which is most of why it tends to beat funds that try.
Inflation
The general rise in prices over time, which means the same money buys less. It compounds, so 3% a year for ten years raises prices by 34%, not 30%.
Interest
The cost of borrowing money, or the payment for lending it. Charged as a percentage of the outstanding amount.
L
Liability
Anything you owe: a mortgage, a car loan, a card balance, money owed to family.
Liquidity
How quickly something can be turned into cash without losing value. A savings account is highly liquid; a house is not.
M
Marginal tax rate
The rate applied to your next dollar of income. Crossing into a higher bracket only taxes the portion above the threshold at the new rate, never your whole income.
Minimum payment
The smallest amount a card issuer will accept in a month, usually a small percentage of the balance plus interest. Because it shrinks as the balance shrinks, paying only it can stretch a balance out for a decade or more.
N
Net worth
Everything you own minus everything you owe. A negative figure is the normal starting position with student debt or a new mortgage; the direction it moves matters more than its sign.
O
Opportunity cost
The value of the best thing you gave up to do what you did. Money used for one purpose cannot be used for another, and the comparison is what makes a choice a real decision.
Option
A contract giving the right, but not the obligation, to buy or sell something at a set price before a set date. Its value drains away as expiry approaches.
P
Portfolio
The whole collection of investments a person holds, considered together.
Principal
The original amount, before interest. On a loan it is what you borrowed; on savings it is what you put in.
Purchasing power
What a sum of money can actually buy. Inflation reduces it even when the number in your account does not change.
R
Return
What an investment gained or lost, as a percentage of what was put in. A total return covers the whole period; an annualized return expresses it as a per-year rate.
Risk
In finance, the range of possible outcomes rather than simply the chance of loss. A higher-risk investment has a wider spread of results in both directions.
Risk-free rate
The return available with essentially no risk of loss, in practice short-term government debt. It is the baseline any riskier investment has to beat to be worth holding.
S
Sharpe ratio
Return above the risk-free rate, divided by volatility. It asks how much return an investment delivered for the amount of bumpiness it put you through.
Stock
A share of ownership in a company. Its value rises and falls with the company's fortunes and with what other people will pay for it.
Strike price
The fixed price at which an option lets you buy or sell the underlying asset.
T
Time value of money
A pound or dollar today is worth more than the same amount later, because today's money can be invested and because inflation erodes future money.
V
Volatility
How much a price moves around, usually measured as the standard deviation of its returns. High volatility means a wide range of day-to-day outcomes, not necessarily a bad investment.
Y
Yield
The income an investment produces each year, as a percentage of its price. A bond's yield is its interest; a share's yield is its dividend.