Many words that have long been considered obsolete are returned to our language. Therefore, it is important to understand the appropriateness of using different words and know all the interpretations of each expression. For example, the adverb is "pretty": the meaning of the word is understandable to almost every connoisseur of literature, but it can be used in different sentences and change its interpretation.
Word interpretation
So, we already mentioned that “fairly” is an adverb, that is, a word that does not change depending on declension. It is considered an outdated and colloquial expression. If you find “pretty” in the explanatory dictionary, the meaning of the word will be ambiguous:
• many;
• for a long time;
• much;
• satisfactory.
The last interpretation is removed from the given series, since the word has not been used in this meaning for a long time.
Fairly: the meaning of the word in Krylov's fable
As you have already noticed, there can be several currents of this expression. However, not all options are listed above. In the study of the adverb “pretty” the meaning of the word will not be fully determined unless you associate it with the adjective “pretty”. In turn, this adjective is interpreted as follows:
• significant in some characteristics (for example, strength or size);
• good or excellent.
From this we can conclude that in some cases “pretty” can mean the same thing as good. In Krylov’s work “Donkey and the Nightingale”, this adverb is used just by analogy with the adjective given above. Donkey telling Nightingale that he was pretty singing, appreciated the sounds made by this bird as good, pleasant to hear.
How is it appropriate to use this word in modern speech?
With the return to modern speech of the expression “fairly”, the meaning of the word has become narrower. It is now inappropriate to use it as good or satisfactory. In a colloquial speech or journalistic article, you can use this adverb as a synonym for a lot of words.
Such a substitution will be understandable to readers or interlocutors and will not unpleasantly stand out. You may have already met this word in the meaning of “many,” but you did not pay attention to it.