They're equivalent ; however the more commonly used phrase 'as well as . .' is more natural.

'In addition to being good-looking, she's also smart.' 'As well as [being] good-looking, she's also smart'.

'She's good-looking in addition to being smart.' 'She's good-looking as well as [being] smart.'

'She's good-looking and additionally she's smart.' 'She's good-looking and she's smart as well.'

Hello -

Additionally and in addition are typically used to begin a sentence or phrase. I use "in addition" more often than "additionally". Both are correct and can be used interchangeably. For example: "My dog costs me a lot money because he had surgery recently. In addition, the dog food is also expensive."

or "My dog costs me a lot money because he had surgery recently. Additionally, the dog food is also expensive."

Paige

I'll put it in math terms, because it's really the only way I understand. Hope it helps.

In addition, or in addition to = x (idea) + y (in addition, or in addition to)

For example: I think that birds are so high, and it's awesome (x, idea). In addition (y), I think birds look super cool also.

You need an idea THEN you can piggy back off the idea with "in addition" (as long as it's relevant).

Addition is literally the action or process of adding something to something else. This varies depending on the context.

For example: The house became bigger with the addition of more rooms.