First of all, quantity in mathematics is a basic concept, which is used to express the size of things, the relationship between sizes and the process of change. Specifically, quantity is a measurable attribute or characteristic, which can be expressed by quantity. For example, length, weight, time, speed, power and temperature are all quantities, which can be described and compared by numbers. Therefore, quantity in mathematics is the basis of numerical calculation and mathematical model, and it is also an important tool to describe natural phenomena and human activities.

Secondly, quantity, as one of the important concepts in mathematics, has many properties and characteristics. Generally speaking, quantity can be measured and calculated by internal attributes and external conditions. For example, the length can be measured with a ruler or measuring instrument, and the weight can be measured with a scale or weighing instrument. In addition, you can also perform operations such as addition, subtraction, multiplication and division, size comparison and unit conversion. These properties and characteristics make quantity widely used and important in mathematics.

The research and application of quantity is one of the important directions of mathematics development. There are different types of quantities in mathematics, such as scalar, vector and matrix, which have different properties and applications. For example, vectors can be used to represent the direction and size of objects, and matrices can be used to describe physical systems and economic models. In addition, in modern science and engineering technology, the measurement and control of quantity is very important, which involves many fields, such as physics, chemistry, biology, digital signal processing and so on. Therefore, quantity in mathematics is the basis and premise of modern science and engineering technology.