The spelling of the word "Onnjelo" is derived from the Esperanto language, which follows certain phonetic rules. The word is pronounced as /onˈjelo/ in IPA phonetic transcription, with stress on the first syllable. The letter "j" in "Onnjelo" represents the phoneme /j/ and is pronounced like the "y" in "yes". The repetition of the letter "n" is a characteristic feature of Esperanto and serves to indicate that the vowel preceding it is pronounced as a separate syllable. Thus, "Onnjelo" is pronounced as "on-ye-lo".