The correct spelling of the term "most half yearly" is "biannually." This word has four syllables, and the stress falls on the third syllable. The IPA phonetic transcription for "biannually" is /baɪ-ˈæn·yu·əl·i/. The "y" sound in the second syllable represents the short "i" sound, and the stress is represented by a raised dot following the stressed syllable. With this spelling, there should be no confusion or ambiguity about the meaning or pronunciation of the word.