In a manner that suggests chirping; with the quality or manner of something that chirps; in a lively or upbeat way.
From 'chirping' (present participle of chirp) + '-ly' (adverb suffix). This creates an adverb from the gerund form, indicating manner performed in the style of chirping.
The '-ing' form of verbs can become adjectives ('chirping birds'), nouns ('chirping is lovely'), or combine with '-ly' to make adverbs ('chirpingly'), showing how English particles like '-ing' are extremely flexible building blocks for creating new word forms.
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