The word "seith" is a Welsh word that is pronounced as /saɪθ/. The word is a variant spelling of "saith," which means "seven" in English. This word is quite unique because it includes the Welsh letter "W." However, this letter is pronounced similarly to the English letter "U." Therefore, the word is pronounced as "sigh-th," with a soft "th" sound at the end. The spelling of the word "seith" may be different from how it's pronounced, but it is an essential aspect of the Welsh language.