Meaning of AN- in English

AN-

an- /ən, æn/ BrE AmE prefix

1 . the form used for ↑ a before a vowel sound

2 . not SYN without :

anarchy (=without government)

anoxia (=a condition caused by lack of oxygen)

Longman Dictionary of Contemporary English.      Longman - Словарь современного английского языка.