Almost every ruling in the rest of these articles reduces to one of three prohibitions. Knowing which one is doing the work in a given case is most of what it takes to reason about a new instrument yourself.
Islamic commercial law starts from unusually broad permission — transactions are lawful unless something specific makes them otherwise — so the interesting content is in the exceptions. Three do most of the work in finance. They are frequently used interchangeably in casual writing, and they are not interchangeable at all: they identify different defects, they apply to different parts of a transaction, and knowing which one is being invoked tells you immediately whether a proposed fix could possibly work.
The most explicitly prohibited of the three, and the least disputed in application. Riba is an increase received for the use of money over time, or for deferral in an exchange, fixed in advance and owed regardless of what happens to the underlying venture. It comes in two families. Riba al-nasi'ah is the interest a lender receives on a loan — the form behind conventional banking, bonds, margin charges and forex swaps. Riba al-fadl is an unequal exchange of the same fungible commodity, the rule underlying the hand-to-hand conditions on currency exchange.
The principle that catches the workarounds is every loan that draws a benefit to the lender is riba — which is why "interest-free" leverage from a broker that profits from the volume it enables is still contested. What riba is not is a prohibition on profit, on financing, or on the time value of money in a sale: a deferred-payment sale may lawfully carry a higher price than a cash one. The objection is to money generating money by itself, detached from any asset or enterprise.
Gharar is excessive, avoidable uncertainty about the substance of a contract: what the object is, whether it exists, whether it can be delivered, or what the price will be. The classic illustrations are selling fish still in the sea or a calf not yet born. It is a defect in the terms, and the qualifiers carry real weight — excessive, because every commercial venture involves uncertainty and Islamic finance requires risk-taking rather than forbidding it, and avoidable, because minor unavoidable ambiguity does not void a contract. This is the prohibition behind the objection to options, whose object is a bare right, and to futures, where neither side is present at contracting. It is also why CFDs are hard to defend: you cannot specify the object of a sale that has none.
Maysir is gambling: a transaction whose outcome turns on chance, in which one party's gain is mechanically the other's loss and nothing is produced. It is a defect in the contract's purpose rather than its terms, which is what distinguishes it from gharar — a maysir contract can be perfectly clear about what happens and still be prohibited. The test that matters in practice is whether wealth is created or merely transferred. A shareholder in a growing company profits because the company produced something; a counterparty on a cash-settled derivative profits exactly what the other side lost. This is why the business-activity screen excludes casino operators outright, and why purely speculative assets with no underlying utility are flagged in crypto screening.
Given an instrument nobody has ruled on, three questions in order get you most of the way. Is there a predetermined return for time? If yes it is riba, and no restructuring of the surrounding contract fixes it. Is it clear what is being exchanged, and can it be delivered? If not it is gharar, which is sometimes curable by specifying the contract properly — salam exists precisely as the cured form of a forward sale. Is anything produced, or is this purely a transfer between two sides of a bet? If the latter, maysir. A fourth question sits underneath all of them and is the one this site's screening actually implements: is the underlying activity itself permissible — because no amount of clean contracting rescues ownership of an impermissible business.
Screening standards are an attempt to make these three operational. A 5% cap on non-compliant revenue and a ~30% cap on interest-bearing debt are riba, expressed as a tolerance for the unavoidable; a business-activity exclusion list is maysir and the prohibited-goods rules, expressed as a gate. Every threshold this site applies, and the standard it comes from, is published in the methodology, with each screened company's real ratios on its own symbol page. Turning a principle into a number is itself a contested act of interpretation — see the minority view in Is Stock Trading Halal?. This is a research tool, not a fatwa — when in doubt, consult a qualified scholar.
Each of the three has its own entry in the Islamic finance glossary — riba, gharar and maysir — alongside the two narrower forms of riba the standards separate, riba al-fadl and riba al-nasi'ah, and the market conduct prohibitions that sit beside them: najash and ihtikar.
See also: All articles · Screening Methodology · Glossary · Is Stock Trading Halal? · Dividend Purification · Not financial or religious advice.