Is *digne* an adverb in the "Munda cor meum" prayer?

Question

Below is one of the prayers which the priest says before reading the Gospel in the Tridentine Mass.

Munda cor meum, ac labia mea, omnípotens Deus, qui labia Isaíæ Prophétæ cálculo mundásti igníto: ita me tua grata miseratióne dignáre mundáre, ut sanctum Evangélium tuum digne váleam nuntiáre. Per Christum, Dóminum nostrum. Amen.

My intuition tells me that digne is an adverb modifying valeam, hence "so that I may worthily be able to announce your holy Gospel." But when I looked up digne in my Latin-English dictionary, it isn't listed as an adverb.

Answer 1

Yes, it is indeed an adverb here. There is also another form of dignus that looks similar, namely the masculine singular vocative. The vocative has a short -e, the adverb has a long one. Using a vocative adjective referring to the God or someone else one is praying to is possible, but does not fit this context.

Many see the adverb as a derived separate word, but I see it more as yet another form of the adjective. The distinction is irrelevant for language usage. These adverbs are easy to form and very productive, so they are not always listed as separate dictionary entries.

Answer 2

It appears that, yes, digne is an adverb. We can often take an adjective and give it an -e ending in order to obtain a corresponding adverb. See this Did grammarians consider the adverbial -e a case ending?