Riba (Interest/Usury): Any guaranteed, predetermined return on a financial transaction regardless of the outcome of the underlying activity. This includes conventional bank interest on savings and loans, credit card interest, and any fixed return that is not tied to actual profit or loss sharing. The Prophet (peace be upon him) cursed the one who consumes riba, the one who pays it, the one who records it, and the two witnesses to it (Muslim).
Gharar (Excessive Uncertainty): Contracts where the terms, subject matter, or outcome are excessively uncertain or ambiguous. This includes selling something you do not own, contracts with unclear terms, and transactions where one party has significantly more information than the other. Some level of uncertainty is natural in business, but excessive gharar that could lead to disputes or exploitation is prohibited.
Maysir (Gambling/Speculation): Any transaction where the outcome depends entirely on chance rather than productive effort. This includes conventional gambling, lottery, and highly speculative financial instruments where gains come purely from price fluctuation without underlying economic value creation.