Both 'in addition to' and 'besides' are correct and can be used to indicate an extra or additional element. 'In addition to' is a little more formal and is commonly used in writing, while 'besides' is slightly less formal and can be used in both spoken and written English.

Both 'in addition' and 'besides' are correct and commonly used to introduce additional information or points. They can be used interchangeably in most contexts, but 'in addition' is slightly more formal than 'besides'. The choice between them depends on the formality of the context.

Beside, without the s, tells us the location of something. Besides, on the other hand, means “in addition,” “in addition to,” “moreover,” or “as well,” depending on context.

'In addition to'...needs 2 facts in the same sentence. e.g. In addition to the high price of a ticket, the ice cream and drinks will cost me $6. BESIDES can also mean "except", and IN ADDITION TO cannot. In spoken English, the words 'besides' has replaced the better word 'beside' in sentences such as: Examples: Nobody has a key besides us.