A digraph is a pair of letters that represent a single sound. Here's why the statement is incorrect:
* Unique Sound: While digraphs often represent a specific sound, it's not necessarily "unique". Many sounds can be represented by different digraphs (e.g., the "sh" sound can be spelled "sh", "ch", "ti", etc.).
* Own Sound: Digraphs don't inherently create their "own" sound. They represent a sound that may be made up of two separate sounds, or a single sound that doesn't exist in isolation.
Example:
The digraph "sh" in "ship" represents the /ʃ/ sound, but this sound isn't unique to "sh". It can also be represented by "ti" in "nation", "ch" in "machine", etc.