The word "heydt" is a German surname that is pronounced as "hahyt" using International Phonetic Alphabet (IPA) transcription. The "h" at the beginning of the word is pronounced as an aspirated sound, similar to the "h" in "hello" or "house". The "ey" in "heydt" is pronounced as the long "a" sound in "day". The "d" is pronounced as a hard "t" sound, and the final "t" is also pronounced in German. Overall, the spelling of "heydt" accurately reflects its German pronunciation.