Here's a breakdown of the typical composition:

* Hydrogen: Makes up about 70-75% of a star's mass.

* Helium: Makes up about 24-28% of a star's mass.

* Trace elements: The remaining 1-2% is a mix of heavier elements, such as carbon, oxygen, neon, iron, and others.

Key factors influencing composition:

* Star's mass: More massive stars have higher temperatures and pressures in their cores, which can fuse heavier elements.

* Star's age: As stars age, they fuse hydrogen into helium, and subsequently, helium into heavier elements. This changes the star's composition over time.

* Star's location: The abundance of elements in the interstellar medium, where stars are born, can influence their initial composition.

It's important to note:

* The composition of a star can vary slightly based on its individual characteristics.

* Stars are constantly evolving and changing their composition through nuclear fusion processes.

Let me know if you'd like more details about specific elements in a star's composition or the processes involved in their formation!