Third person singular present tense of 'chirk,' meaning he/she/it makes cheerful chirping or clicking sounds.
From 'chirk' with the third person singular '-s' ending, following the standard English present tense conjugation pattern.
That simple '-s' on the end is doing enormous grammatical work—it tells you it's present tense, singular subject, and third person, all at once, which is why English learners struggle so much with this tiny letter that packs such a punch.
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