Question

what is the pural form of el nino

Answer 1

Los niños.

It can mean "the boys," or "the children."

Answer 2

@ettenelalovesnutella

If you're talking about oceanography, then you're right, because the proper noun "El Niño" refers to a phenomenon.

I answered batmanismyhero12's question from a Spanish language perspective, because this is the Language and Culture section.

In Spanish, "el niño" is a common, singular noun. It can mean "the boy," or "the child."
So, "los niños" is the common, plural noun. It can mean "the boys," or "the children."