Add/Remove Drop Down Items

Add/Remove Drop Down Items

Are we able to add/remove drop down items via script? I do not want to make a Lookup field, but simply be able to add an item to an existing drop down field upon user input. This is most likely a beginner question, but every time I look for the solution I can only find Lookup field tutorials, so thank you for your patience.

Please let me know if this is possible!

Thank you in advance!