# Function Conjunction → The Anatomy of a Physical Expression

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Factors serve as The Anatomy of a Physical Expression. They come in several types as listed below, each characterized as having a distinct role in defining a property of a physical system. The following list items are partially underlined to make memorization easy:

1. Constants
2. Coefficients
3. Quantities
4. Proximities
5. Dislocations
6. Directions

## Definition

### Constants

• = Speed of Light
• = Gravitational constant
• = Boltzmann's constant
• = Fine Structure constant
• = Magnetic Permeability of Free Space
• = Electric Permittivity of Free Space

### Coefficients

• = Relative Magnetic Permeability
• = Relative Electric Permittivity

### Quantities

• = point charge
• = linear charge density (for continuous charge)
• = surface charge density (for continuous charge)
• = volume charge density (for continuous charge)
• = mass
• = volume mass density

### Proximities

• = inverse of the magnitude of the separation between positions and
• = inverse square of the magnitude of the separation between positions and

### Dislocations

• = position
• = velocity
• = acceleration

#### Dislocations according to an inertial observer at time

• = position of a charge at time , when it receives a light signal from that was emitted earlier at the retarded time
• = = velocity of a charge at time , when it receives a light signal from that was emitted earlier at the retarded time
• = = acceleration of a charge at time , when it receives a light signal from that was emitted earlier at the retarded time
• = position a charge had at the retarded time , when it emitted a light signal which has now reached at position and time
• = = velocity a charge had at the retarded time , when it emitted a light signal which has now reached at position and time
• = = acceleration a charge had at the retarded time , when it emitted a light signal which has now reached at position and time

### Directions

• = position unit vector
• = velocity unit vector
• = acceleration unit vector

#### Directions according to an inertial observer at time

• = position unit vector of at time
• = velocity unit vector of at time
• = acceleration unit vector of at time
• = position unit vector of at retarded time
• = velocity unit vector of at retarded time
• = acceleration unit vector of at retarded time