A rule of thumb is an informal rule of thumb that contains simplified rules that apply in most situations.
In finance, there are many rules of thumb that tell you how much to save, how much to pay for a house, where to invest, and so on.
Rules of thumb are not scientific and do not take into account individual circumstances and human needs, so they may not apply to your particular situation.
The bid-ask spread is the difference between the highest price a buyer is willing to pay for an asset and the lowest price a seller is willing to accept.
Preliminary analysis in financial markets refers to the forecasting of various indicators, economic and financial, by evaluating past and present data and parameters.
A good delivery is understood as an unhindered transfer of ownership of a security from the seller to the buyer in compliance with all necessary requirements.
Risk takes many forms, but is generally classified as the possibility that the outcome or actual return on an investment will differ from the expected outcome or return.