The word "ad def an" is actually spelled "adhesion", with the IPA phonetic transcription /ædˈhiʒən/. This word refers to the sticking together of two surfaces, typically due to an adhesive substance. The spelling of the word can be broken down into its constituent sounds: /æ/ for the "a" sound, /d/ for the "d" sound, /h/ and /ʒ/ for the "h" and "j" sounds pronounced together as one, and /ən/ for the "n" sound with a schwa vowel sound in the middle. Proper spelling is important for communication and clarity in writing.