How is "specific learning disability" (SLD) best defined?

Specific Learning Disability (SLD) is best defined as a disorder that significantly impacts an individual's ability to understand or use spoken or written language. This definition encompasses a range of difficulties that can affect academic skills, including reading, writing, and mathematics. Individuals with SLD may have challenges such as dyslexia, which affects reading, or dyscalculia, which impacts mathematical skills.

The focus on the understanding and use of language is crucial since SLD is characterized by discrepancies between an individual's potential and their academic performance, often leading to difficulties in processing information or communicating effectively. Therefore, choice C accurately captures the essence of what constitutes a specific learning disability.