The Tip of Your Tongue
The word is there. The path to it isn't.
Memory has two parts: storage and retrieval. When a word is stuck on the tip of your tongue, the memory is intact, but the path to it is temporarily blocked, often because a similar-sounding word is getting in the way. That's why you can sense the word's shape (its first letter, its rhythm) without being able to produce it.
This happens to everyone, in every language and at every age. The word almost always arrives later, usually when you've stopped trying. You're in the shower, or driving, or halfway through an unrelated conversation, and it simply appears. Your brain didn't quit searching when you did. It kept working the problem in the background until the interference cleared.
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The Tip of Your Tongue