What long and short mean

Two positions are opened on the same instrument, at the same price, at the same moment, in the same size. An hour later the price is higher. One is showing a gain and the other a loss of exactly the same size. The instrument did not do two different things. The contracts differ in one field, recorded when each opened, and that field is what long and short name.

Direction is a property of the contract 

A contract for difference settles the difference between the price at which it opened and the price at which it closed, calculated on the full contract value. Direction is the sign convention attached to that settlement, and it is decided once, at the moment of opening.

A long position settles in favour of its holder when the closing price is higher than the opening price, and against its holder when the closing price is lower. A short position settles in favour of its holder when the closing price is lower, and against its holder when it is higher. That is the entire definition. It contains no forecast and no sentiment.

The two ideas get used as if they were one. A position is not long because its holder is optimistic. It is long because the direction field says long, and it settles by that rule whether or not the opinion behind it lasts the afternoon. The words predate the instrument: a merchant with a surplus was long of it, and one who had sold goods not yet in hand was short of a delivery.

Working out which way the money goes 

One formula covers both directions. The result of a closed position is the closing price less the opening price, multiplied by the size of the contract, with the sign reversed if the position is short. Everything else about the two tickets is identical.

The four cases form a square: contract direction down one axis, market direction across the other. Same magnitude in every cell, sign reversed on the diagonal. No side of it is the gentler one.

Why a short position borrows nothing 

In the share market the vocabulary came from, selling something not owned is a piece of machinery. The seller borrows the shares, delivers them to the buyer, pays a fee for every day the loan stays open, and buys them back later to return them. It exists because a real security has to reach a real buyer, and it imposes real limits: an instrument with few willing lenders is expensive to borrow, or impossible.

A CFD carries none of it, for the reason the previous lesson set out. Nothing is delivered, so nothing has to be found first. The parties settle a difference in cash, and a difference settles in either direction without anyone holding the underlying. Opening short is procedurally identical to opening long: same instrument, same ticket, same margin arithmetic, one field different. A short position is not a bet placed backwards. It is the same contract with the other sign.

The one real asymmetry, and where it comes from 

Within any single move the arithmetic is symmetric, as the square shows. Across the whole range of available moves it is not, and the reason is a boundary rather than a belief about markets. A price cannot fall below zero, so the largest adverse move available to a long position is the whole of the price. A price has no upper boundary, so no such ceiling exists on the adverse side of a short.

Trading literature renders this as the loss on a short being theoretically unlimited, and the word carrying the weight is theoretically: it describes the absence of an arithmetic bound, not an expectation about any instrument. Practitioner traditions disagree over what the boundary deserves. One treats it as a first-order difference between the directions. Another treats it as near irrelevant over hours, because the paths reaching an unbounded loss and the paths reaching a close-out are the same paths, and the close-out arrives first. This page holds neither view.

Neither direction limits a loss to the deposit 

That boundary concerns the far end of the range, not the size of an ordinary loss. Profit and loss on a CFD are calculated on the full contract value while only a percentage of that value is held as margin against it. An adverse move worth more than the margin therefore produces a loss larger than the margin, and a loss on a CFD position is not limited to the amount deposited. That is true of a long and a short identically. Close-out procedures exist and are the subject of a later module, but a procedure is not a guarantee: a market that gaps can carry a position past the level that triggered one.

Closing is the same act with the sign reversed 

An open position is closed by an equal and opposite contract in the same instrument. A long of one lot is closed by a contract to sell one lot, a short of one lot by a contract to buy one lot. At that moment the difference is settled and the position stops accruing anything, financing included.

This is where an expensive confusion lives. A sell control does two different jobs depending on what is already open: with nothing open it opens a short, with a long open it may instead close that long. Platforms resolve the ambiguity differently, and the resolution is an account setting rather than a fact about the market. Some net every contract in one instrument into a single position, so an opposite ticket reduces or closes what exists. Others hold each ticket separately, so an opposite ticket opens a second position facing the other way, both open and each financed on its own.

A third state has a name. A trader holding no contract in an instrument is flat, which is not a direction and not a quiet third opinion. It is the absence of the contract, so nothing settles and nothing accrues.