Factors affecting the frequency stability of an oscillator are temperature variation, inter-element capacitances and stray capacitances, and coil size.

Temperature Variation:
- Temperature variation is a major factor that affects the frequency stability of an oscillator.
- Changes in temperature can cause the physical dimensions of the oscillator components to expand or contract, leading to a change in the oscillator's frequency.
- For example, if the temperature increases, the components may expand, resulting in an increase in the frequency of the oscillator.
- Conversely, if the temperature decreases, the components may contract, leading to a decrease in the frequency of the oscillator.
- Therefore, temperature stability is crucial for maintaining the desired frequency stability of an oscillator.

Inter-Element Capacitances and Stray Capacitances:
- Inter-element capacitances refer to the capacitance between different components or elements of the oscillator circuit.
- Stray capacitances, on the other hand, refer to the unwanted capacitances that exist in the circuit unintentionally.
- Both inter-element capacitances and stray capacitances can affect the frequency stability of an oscillator.
- These capacitances can introduce additional reactance into the circuit, which can alter the frequency response of the oscillator.
- The presence of capacitances can cause the oscillator frequency to deviate from the desired value.
- Therefore, minimizing inter-element capacitances and stray capacitances is essential for maintaining frequency stability.

Coil Size:
- The size of the coil in an oscillator circuit can also impact frequency stability.
- The inductance of a coil is directly proportional to its size.
- A larger coil will have a higher inductance, which affects the resonant frequency of the oscillator.
- Changes in coil size can result in a change in the oscillator frequency.
- Therefore, maintaining a consistent coil size is important for frequency stability.

In summary, temperature variation, inter-element capacitances and stray capacitances, and coil size are all factors that affect the frequency stability of an oscillator. Temperature stability is crucial to prevent changes in physical dimensions of the components. Minimizing inter-element capacitances and stray capacitances is important to avoid unwanted reactance. Maintaining a consistent coil size helps to maintain a stable resonant frequency. By considering and managing these factors, the frequency stability of an oscillator can be maintained.