What is Einstein syndrome?
“Einstein syndrome is a condition where a child experiences late onset of language, or a late language emergence, but demonstrates giftedness in other areas of analytical thinking. A child with Einstein syndrome eventually speaks with no issues, but remains ahead of the curve in other areas.”
https://www.healthline.com/health/einstein-syndrome#what-it-is
Edward Teller did not speak at all until after his third birthday.
When he did finally speak, it was complete sentences.