The easiest way to describe how person-first language is used in relation to autism is to read these two sentences:

Person-first: I have autism.

Identity-first: I am an autistic person.

I personally choose to say that I am an autistic person – identity-first. I remember speaking to someone at an anxiety group who is autistic and I really felt we understood each other (I was yet to have the grand reveal of an autistic diagnosis at that point). I said ‘What is it you have again?’. I made it sound like she had a terrible disease that she was trying to recover from. I still cringe about that, though we now have a lovely friendship as a result of me daring to approach her!

It really is a matter of personal choice as to which you prefer. In the UK, identity-first language is more commonly preferred by autistic people and less commonly preferred by medical professionals, though this is by no means the rule. The most important thing here is that you feel comfortable with the language you choose to use, because you’ll probably be saying it quite a lot!