ac
This might be just a supplemental entry adding to an entry in the Main Volume.
Related §§ in Wright's OE Grammar:
In the OE text, the length is:indicated by acute accentsindicated by macronsnot indicated.
ac
AddNo ðæt án ðæt . . . ac (eác), Bt. 21; F. 74, 18: 5, 3; F. 14, 7. Ah ðeáhhwæðre, Past. 305, 1. Nis ðæt mín miht, ac gif (unless ) ðú gelýfest. Ðá cwæð hé tó him : 'Ac tó hwon sweriað git mán?', Guth. 64, 5 : 74, 5. Hwæt gelamp ðé nú ðá? ac ðé on ðysse nihte sum untrymnys gelamp?, 80, 16.
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A Combined List of Abbreviations.

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A Combined List of Abbreviations.