prefix
or ap- or aph-
Etymology: apo- from Middle English, from Middle French & Latin; Middle French, from Latin, from Greek, from apo; ap- from Greek, from apo; aph- from Late Latin, from Greek, from apo — more at of
1. : away from : off
ap astron
ap helion
2. : detached : separate
apo carpous
3. : formed from : related to — in names of chemical compounds
apo codeine
— apo- before consonants other than h and sometimes ap- before vowels and aph- before h (which is not repeated) but frequently apo- even before h or a vowel