The word "achenial" is spelled with the letter combination "ch" because it is derived from the Latin word "achenium" which also contains this sound. The IPA phonetic transcription for "achenial" is /əˈkiːniəl/. The first syllable contains an unstressed schwa sound followed by a long "e" vowel sound. The second syllable begins with a hard "k" sound followed by a short "i" vowel sound and ends with the sound "əl". The final syllable is unstressed and contains the sound "əl".