Dyslexia is one of a handful of overlapping Specific Learning Difficulties (SpLDs) which involve cognitive processing differences.
Dyslexia basically means unexpected difficulty with the written word because of specific processing differences. It can but does not always involve difficulty learning to read or spell or both. It can but does not always involve lack of reading fluency or slow or disorganised writing. It can also involve disorganised thought processes, difficulty keeping up with fast paced verbal input in class or difficulty retaining what is being read, heard or planned for writing. It can involve any or all of these difficulties to a greater or lesser extent.
This means that no two dyslexic students are the same. You don’t have to struggle with phonics to be dyslexic. You could love reading and still be dyslexic. So the term itself is useful to an extent in classifying the broad nature of a student’s difficulty, but more useful is to know for each student what their individual profile of strengths and weaknesses is and how these are affecting their learning. Early exposure to books and being read to, interest in learning, certain types of teacher and certain personality traits such as determination or patience all have an impact on the extent to which any underlying dyslexic type difficulties have a noticeable effect on school or college work.
That is why some students with dyslexia are picked up very young and others are not identified until A Levels or beyond.
There are other, overlapping Specific Learning Difficulties with some similar processing weaknesses. Dyspraxia (or Developmental Coordination Disorder), Attention Deficit Hyperactivity Disorder, Speech and Language Difficulties and Autism can also be described as SpLDs, although these can also affect broader areas of life and are usually diagnosed by a medical professional. But the point is that often, people are not clearly one thing or another but can have a few traits from more than one defined difficulty. That means that students who have first been identified to have coordination difficulties may be diagnosed as such, but not be identified as having co-occurring dyslexia for example. Certain cognitive processing difficulties, such as slow processing or weak working memory can be present across several different SpLDs, which is what leads to students with different diagnoses having similar issues with mental organisation and retention of information, for example.
The prime cognitive processing weaknesses which suggest dyslexia specifically are difficulty working with sounds in words (weak phonological awareness), difficulty remembering sound information, slow naming speed (a type of verbal processing speed required for reading fluency and efficient mental processing) and often, relatively weak working memory.