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Brief

A dimension is something that can be measured in order to quantify a physical parameter such as energy, voltage, or force, or mass flow rate.

A primary dimension is a dimension that is not derivable from other dimensions. All dimensions can be built from a set of 7 primary dimensions.

Details

(from Gemini AI)

A primary dimension, also known as a basic or fundamental dimension, is one of the independent dimensions in a system of measurement.1 These dimensions are considered fundamental because they are not derivable from other dimensions. All other physical quantities and their associated dimensions can be expressed as combinations of these primary dimensions.

Think of them as the basic building blocks for describing the physical world in a measurable way. Just like you can combine basic colors to create a wide range of other colors, you can combine primary dimensions to describe more complex quantities.

There are seven primary dimensions recognized by the International System of Units (SI), which is the most widely used system of units:

1. Mass (M): Represents the amount of matter in an object.
2. Length (L): Represents spatial extent.4
3. Time (T): Represents duration.5
4. Amount of matter (N): Represents the number of entities (like atoms or molecules) in a sample, measured in moles.
5. Luminosity (J): Represents the power emitted by a light source.
6. Temperature (Θ): Represents the degree of hotness or coldness of a substance.
7. Electric current (I): Represents the rate of flow of electric charge.6

These primary dimensions form the foundation for understanding and quantifying physical phenomena. They are essential for dimensional analysis, which is a powerful tool used in science and engineering to check the consistency of equations and to derive relationships between physical quantities.