ap-1

1.
variant of ad- before p: appear.

ap-2

1.
variant of apo- before a vowel or h: aphelion.
British Dictionary definitions for ap-

ap-

prefix
1.
a variant of apo- aphelion

apo-

prefix
1.
away from; off: apogee
2.
indicating separation of: apocarpous
3.
indicating a lack or absence of: apogamy
4.
indicating derivation from or relationship to: apomorphine
Word Origin
from Greek apo away, off
Word Origin and History for ap-

form of Latin ad- before words beginning in -p-; see ad-.

patronymic prefix in Welsh names, earlier map "son," cognate with Gaelic mac. Since 17c. merged into surnames (Ap Rhys = Price, Ap Evan = Bevan, etc.).

It is said that a Welshman who evidently was not willing to be surpassed in length of pedigree, when making out his genealogical tree, wrote near the middle of his long array of 'aps' -- "about this time Adam was born." ["Origin and Significance of our Names," "The Chautauquan," Oct. 1887-July 1888]

ap- in Medicine

ap- 1
pref.
Variant of ad-.

ap- 2
pref.
Variant of apo-.