Question: ad infinitum how do you say it?
Answer: The 'new' or 'modern' way of saying 'ad infinitum' follows modern pronunciation rules, and has become correct by usage. It is: 'ad in/fi/NI/t[e]m', with the capital 'I' sounding like 'eye', and a neutral vowel on the 'u'. (A neutral vowel makes an 'uh' sound like the 'a' in 'China', and the 'e' in 'the').