The word "thIDAth" is a peculiar example of English spelling. Despite its unusual appearance, it is simply the word "the" followed by the letters "IDA" and then "th". The "th" at the end is pronounced as in "math" or "bath", while the "ID" is pronounced as in "kid" or "bid". The final "A" is pronounced as in "cat". Therefore, the correct IPA spelling of the word is /ðəˈaɪdæθ/. This illustrates how English spelling can be idiosyncratic, as it often reflects the complex history of the language.