Here are three separate metaphors:
1. A linear continuum (like wavelength for light) from "no autism" to "really bad autism".
2. A collection of disjoint sets (like individual named colors like "cyan" and "puce") for cases like "really into trains autism", "freaks out at parties autism", "non-verbal autism", etc.
3. A continuous mixture of different properties (like rgb(.1, .2, .05)) for symptoms like "10% social dysfunction", "20% repetitive behavior", "5% sensory overstimulation".
When people describe autism as a spectrum disorder, they generally mean the third metaphor. It's a mixture of different symptoms and different autistic people have different amounts of those symptoms but all people diagnosed with autism have a significant amount of them and their symptoms will have some amount of overlap with other autistic people.
1. A linear continuum (like wavelength for light) from "no autism" to "really bad autism".
2. A collection of disjoint sets (like individual named colors like "cyan" and "puce") for cases like "really into trains autism", "freaks out at parties autism", "non-verbal autism", etc.
3. A continuous mixture of different properties (like rgb(.1, .2, .05)) for symptoms like "10% social dysfunction", "20% repetitive behavior", "5% sensory overstimulation".
When people describe autism as a spectrum disorder, they generally mean the third metaphor. It's a mixture of different symptoms and different autistic people have different amounts of those symptoms but all people diagnosed with autism have a significant amount of them and their symptoms will have some amount of overlap with other autistic people.