плечо - плечи

I would expect the nominative plural to be: плечa.
Are their many neutral nouns that form the plural in this way?

I can be wrong, but I believe that’s remains of the dual.
In Old Russian there were 3 grammatical numbers: singular, dual, and plural. In modern Russian there’s no dual anymore, but some words use old dual forms for the plural. In most cases, those are words denoting some paired objects, especially body parts.

The ending -и was used for some neuter nouns’ dual. The stems ending with velar consonants were exposed to palatalization: к → ч, г → ж, х → ш.
плечо́ → пле́чи
о́ко → о́чи
у́хо → у́ши

The ending -а was used for some masculine nouns’ dual:
глаз → глаза́
рог → рога́
бок → бока́

Quote:

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Originally Posted by Soft sign

I can be wrong, but I believe that’s remains of the dual.
In Old Russian there were 3 grammatical numbers: singular, dual, and plural. In modern Russian there’s no dual anymore, but some words use old dual forms for the plural. In most cases, those are words denoting some paired objects, especially body parts.

The ending -и was used for some neuter nouns’ dual. The stems ending with velar consonants were exposed to palatalization: к → ч, г → ж, х → ш.
плечо́ → пле́чи
о́ко → о́чи
у́хо → у́ши

The ending -а was used for some masculine nouns’ dual:
глаз → глаза́
рог → рога́
бок → бока́

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Excellent analysis soft sign. I am tempted to ask what is your profession.

I’m a programmer :)