I usually use the term "spectrum" or "ASD" because it includes many different disorders, whereas "Aspie" is much more specific and doesn't describe everyone.
I sometimes refer to myself as having ASD because I don't know exactly where on the spectrum I fall.
I also sometimes prefer ASD because, on the rare occasion that I actually disclose that personal information to someone new, I feel like it doesn't carry the same negative stereotypes that "Autism" does.
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I'll brave the storm to come, for it surely looks like rain...