がたい is used to describe actions that are emotionally or practically hard to do. It often appears with verbs like 信じる (to believe), 許す (to forgive), 理解する (to understand), or 耐える (to endure). For example, 信じがたい means 'hard to believe', and 許しがたい means 'unforgivable'. This pattern is more formal and is commonly found in written language, such as news reports or essays, rather than in casual conversation.

Unlike にくい, which also means 'difficult to', がたい emphasizes that the difficulty comes from a deep sense of reluctance or impossibility, not just physical difficulty. For example, この本は読みにくい means 'this book is hard to read' (because of font or complexity), but 読みがたい would imply you cannot bring yourself to read it (e.g., due to emotional content).