I am obviously not a doctor or any kind of autism specialist for that matter.
On this page I will include a 'basic' definition of what autism is ,as well as some of the 'indicators' that someone may be autistic. I feel this is important as I know some people who visit this site may be investigating if they or someone else they know could be autistic.

Even after reading this information I must emphasise that anyone who thinks that they may be autistic must go through a proper assessment and diagnosis.

A Basic Definition of Autism

Autism can be defined as a lifelong, developmental condition that affects the way a person communicates, interacts and processes information. It also affects how an individual makes sense of the world around them. Autism is a spectrum, which means that each individual with autism shares common difficulties in social communication and restrictive or repetitive patterns of behaviour or interests, however the level of severity across these difficulties will impact on individuals in different ways.

In the past autism was often categorised in many different ways. People like myself may have been described as having 'high functioning autism' or 'Aspergers Syndrome'.
Aspergers Syndrome was named after an Austrian paediatrician Hans Asperger (new evidence in 2018 about his problematic history during WWII has led to a reluctance to still use this term). It is my understanding that the preferred terminology is now to say that someone is on the 'Autistic Spectrum' or has an 'Autistic Spectrum Disorder'. Although it must be noted that some people are still happy to identify themselves as having Aspergers or even call themselves an 'Aspie'.

Signs of Autism

Because Autism is a spectrum disorder, it can range from very mild to very severe and occur in all ethnic, socioeconomic and age groups. It has been found that males are four times more likely to have autism than females.

A person with ASD might:

Not respond to their name (they may appear deaf)
Not point at objects or things of interest, or demonstrate interest
Avoid eye contact
Want to be alone
Have difficulty understanding, or showing understanding, of other people’s feelings or their own
Have no speech or delayed speech
Repeat words or phrases over and over (echolalia)
Give unrelated answers to questions
Get upset by minor changes
Have obsessive interests
Flap their hands, rock their body, or spin in circles
Have unusual reactions (over or under-sensitivity) to the way things sound, smell, taste, look, or feel
Have low to no social skills
Avoid or resist physical contact
Demonstrate little safety or danger awareness
Reverse pronouns (e.g., says “you” instead of “I”)

People with autism may also:

Have unusual interests and behaviours
Have extreme anxiety and phobias, as well as unusual phobias
Line up objects
Like parts of objects (e.g., wheels)
Become upset by minor changes
Have obsessive interests

Other Symptoms:

Hyperactivity (very active)
Impulsivity (acting without thinking)
Short attention span
Causing self injury
Unusual eating and sleeping habits
Unusual mood or emotional reactions
Lack of fear or more fear than expected
Have unusual sleeping habits

As you can see from the list there are many possible indicators that someone could be autistic. These signs will obviously vary, in both type and severity, from person to person. This list in itself may not even be exhaustive and I may have missed some out!

Please don't be panicked by the range and number of things listed, as they are certainly not all negative. Some are often seen as being a strength of being autistic and in fact some companies (particularly in I.T. I believe) often seek out autistic people to employ.