This is a great question. The answer is fairly complex and has changed somewhat over the years. Historically, a learning disability (LD) was defined as a statistical difference between a person's thinking abilities and their academic skills (e.g., reading, writing, and math). There had to be a gap of a certain size before a person was said to qualify as having and LD. This previous way of defining LD's was helpful when trying to determine when and where to support a student with a reader, scribe, or calculator. However, it did not provide all the information to help the individual develop skills or understand their learning profile.
We now understand LD's to be a neurological, or brain-based processing issue; weaknesses in an area of processing (e.g., speed or memory) that make learning basic skills or complex learning problematic. The Learning Disabilities Association of America (https://ldaamerica.org/types-of-learning-disabilities/) provides comprehensive criteria and assessment processes that we follow. The above link offers more information about the various forms of LD's.
An assessment of learning can only be done by examining an individuals cognitive abilities, academic skills, background/medical history, family history, and exposure or opportunities to learn. Social emotional and attention difficulties are typically explored as possible alternatives, contributing factors, or additional concerns, as these are very common in individuals with learning differences, and can often become a challenge when learning disabilities have gone undiagnosed or unsupported for some time. They can also look like LD's when LD's are not in fact present.
If you think you or your child may have a learning disability, or some challenge affecting learning, a psychologist can help you understand the profile and possibilities of such challenges. With a comprehensive assessment, an individual can move forward with a plan and supports in place to help them achieve their goals and succeed in life.
Please be in touch if you have any questions or would like more information.