verb..present tense..perbuatan tambah s

mengapa di dalam Present Tense , verb adakalanya ditulis dengan kata asal dan adakalanya ditambah huruf s di penghujung perkataan tersebut?
e.g. eat adakala ditulis eats?

penjelasan:

Abu eats nasi lemak every day.
He eats nasi lemak every day.
She eats nasi lemak every day.
It eats fish every day.

kata asal utk makan adalah eat.Ditambah s menjadi eats sebab tukang buatnya seorang (SINGULAR). Abu , he, she , it ( seorang..singular).

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Abu and Ani eat nasi lemak every day.
They eat nasi lemak every day.
We eat  nasi lemak every day

eat akan tetap dengan ejaan asal jika tukang buat lebih dari seorang (PLURAL)

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I dan You akan guna eat. I dan You ni special case.

I eat nasi lemak every day.
You eat nasi lemak every day.