Market terms: spread, mid-market rate, peg, liquidity, slippage

Spread

One sentence: the spread is the gap between the price at which the market buys and the price at which it sells, and it is how the other side earns a living.

The long read. A quote on an exchange screen is never one number — it is two, and the distance between them is somebody’s wage. When you sell USDT, you are paid the lower number; when you buy, you pay the higher one. Multiply that distance by the volume of a busy counter and you understand why spreads, not luck, keep exchange desks open. A narrow spread usually signals a liquid, competitive market; a wide one signals either a thin market, an unusual hour, or a counterparty that has decided today is the day your urgency pays for their rent.

The practical consequence is that comparing offers by “rate” alone is a beginner’s tax. Two desks can quote the same headline number while their spreads differ, and the difference lands on your side of the deal. A habit of asking for both sides of the price — or of reading the structure of an offer before accepting it — costs nothing and compounds over every future transaction. For a worked view of how honest offers are compared, the practical exchange write-ups on UsdtChange walk through the arithmetic without selling anything.

Mid-market rate

One sentence: the mid-market rate is the arithmetic middle between the buy and sell price, a reference point that almost nobody actually trades at.

The long read. Search engines and data aggregators love displaying a single reference rate for USDT against a fiat currency; it looks like the price. It is not an offer. It is the midpoint of the two-sided market — the number you would get if the spread did not exist, which it always does. Treating the mid-market rate as a promise is the single most common way people conclude they were cheated when, mechanically, they simply crossed a spread they had never been told about.

A disciplined reader uses the mid-market rate as a ruler, not a destination: it tells you how far an offered price sits from the middle, and therefore how much of the distance is the market’s honest cost versus somebody’s margin. When an offer sits suspiciously far on the favourable side of the middle, the question to ask is not “where do I sign” but “what does the counterparty know that I do not” — a question the catalogue of exchange directions on CryptoChange helps structure by comparing how different directions are normally priced.

Peg

One sentence: a stablecoin’s peg is the declared intention to keep one token worth one unit of fiat, maintained by mechanisms rather than by promises.

The long read. USDT is designed to hover near its reference currency the way a ferry hovers near its dock — close, but never bolted. On liquid markets the deviations are usually small and brief, arbitraged away within minutes; on thin markets, at odd hours, or during stress, the same token can trade a fraction of a percent away from its anchor for hours. That fraction is invisible in a screenshot and perfectly visible in a ledger.

The peg is also why “stable” never means “riskless”. The word describes an engineering goal, not a law of nature: reserves, redemption mechanics and market confidence all sit underneath it. For everyday purposes the lesson is modest — check the actual traded price of the moment rather than the word on the label, and treat any exchange that quotes a mysteriously perfect rate, immune to the day’s wobble, with the suspicion it has earned.

Liquidity

One sentence: liquidity is how much you can trade before your own order starts moving the price against you.

The long read. Liquidity is the market’s shock absorber. In a liquid market your order vanishes into a crowd of counterparties at the quoted price; in an illiquid one your order is the event, and the price bends around it. This is why the same coin, at the same second, can cost meaningfully different amounts on a major venue and a small regional desk: they are not quoting different opinions, they are quoting different depths.

Size is what converts liquidity from a textbook word into your problem. An amount that is routine for one market is a liquidity event for a smaller one, and the polite term for the damage is slippage — the next entry. Before moving a large sum, the honest question is not only “what is the rate” but “how much of this can this venue absorb at that rate”, and the honest answer usually involves splitting the transfer or choosing a deeper pool.

Slippage

One sentence: slippage is the difference between the price you were shown and the price your transaction actually received.

The long read. Slippage is what happens when a quote meets reality. It appears in fast markets, thin markets and large orders — anywhere the price can move between the moment you approve a transaction and the moment it executes. It is not always a scam: in a genuinely volatile minute, honest slippage is the market passing its own turbulence on to you. What distinguishes tolerable slippage from abuse is predictability: a venue that discloses its execution rules in advance is passing on the weather; one whose quotes routinely drift only in its own favour is manufacturing it.

The defence is arithmetic done before commitment. If you can calculate the worst tolerable outcome of a transaction — and decline anything that cannot state it — slippage stops being a surprise and becomes a priced-in cost. The habit matters most where markets are thinnest: exotic directions, holiday hours, and amounts that make you the biggest fish in a small pond.

The shelf in one glance

Five entries, one mechanism: prices are two-sided, the middle is a mirage, stability is engineered, depth is finite, and execution is a moment in time rather than a screenshot. Read together, the market shelf explains most of what people call “bad luck” in exchange.

• Spread — the two-sided gap that pays the other side’s rent.
• Mid-market rate — a reference ruler, never an offer.
• Peg — an engineered intention, not a law of nature.
• Liquidity — how much the pond can swallow before it bends.
• Slippage — the distance between the shown price and the real one.