A figure of merit (FOM) is a value used to evaluate the performance of a system or device. It is a quantitative measure that is used to compare different options or alternatives in order to determine which one is the best or most suitable for a particular application. Figures of merit are often used in the field of engineering to compare the performance of different designs or technologies, and can be used to optimize the performance of a system or device by identifying the factors that most influence its performance. Examples of figures of merit include energy efficiency, speed, accuracy, and cost. A figure of merit is a particular metric that is commonly used to judge the value of a product or service. Fuel efficiency ratings such as Miles Per Gallon (MPG) are commonly used to compare cars.

There are many different figures of merit that can be used to evaluate the performance of a system or device, depending on the specific application and the factors that are most important in that context. Some examples of figures of merit include:

• Energy efficiency: This is a measure of how much energy a device or system uses in relation to its output or the work it performs. A high energy efficiency means that the device or system uses less energy to produce the same amount of output, and is therefore more cost-effective and environmentally friendly.
• Speed: This is a measure of how quickly a device or system can perform a specific task or process. High speed is often desirable in applications where time is a critical factor, such as in high-speed communication systems or fast-moving manufacturing processes.
• Accuracy: This is a measure of how closely a device or system can produce the desired result. In applications where precision is important, such as in scientific measurements or medical imaging, a high accuracy figure of merit is essential.
• Cost: This is a measure of how much a device or system costs to produce, operate, or maintain. In many cases, cost is an important factor in choosing the best option, and a low cost figure of merit can make a technology or design more attractive.

Other figures of merit that are commonly used in engineering include reliability, durability, flexibility, and power consumption.