Kc 50

[Kaccāyanabyākaraṇaṃ, Sandhikappa, Pañcamakaṇḍa, Sutta 50]

50. 45. O avassa (126).

Ava icc' etassa byañjane pare kvaci okāro hoti.

When a consonant follows, sometimes there is the substitution of ‘ava’ for
     ‘o’.

[. . . sometimes 'o' is substituted for 'ava'. --ja]

Andhakārena onaddhā (Khu. i, 35).

Example:
onaddhā: ava naddhā; o naddhā (50); onaddhā.

Kvacī ti kasmā? Avasussatu me sarīre maṃsalohitaṃ (M. ī, 146).

Why say ‘sometimes’? To prevent the operation of this rule in the following:
Avasussatu me sarīre maṃsalohitaṃ.

Counter Examples:
avasussatu. Here there is no substitution of ‘ava’ for ‘o’.

-- translation by Ven. U Nandisena, 2004

-- posted (with some minor editing) by Jim Anderson, 28 December 2010
    (last quarter moon, 4:18 GMT)