A regional or dialectal pronunciation and spelling of 'height,' sometimes considered nonstandard but persisting in some American English dialects.
This pronunciation likely arose through analogy with words like 'width' and 'breadth,' where the ending sound is 'th'—speakers unconsciously applied this pattern to 'height,' creating a rhyming set.
Linguists call this 'analogical extension'—speakers' brains are pattern-recognition machines, so 'heighth' reveals how English learners naturally regularize irregular word families, even after 500 years of standardization.
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