The word "guertin" is spelled with a "ue" combination, which makes the "u" part of a diphthong vowel sound. In IPA phonetic transcription, it would be written as /ɡɜrtɪn/. This means that the "g" is pronounced as a hard "g" sound, the "er" combination is pronounced as an "ur" sound, the "t" is pronounced as a hard "t" sound, the "i" is pronounced like an "ee" sound, and the "n" is pronounced as a hard "n" sound.