Why bisons the correct plural of bison?

The correct plural of "bison" is bison, not bisons. This is because "bison" is a word that has a zero plural, meaning it doesn't change form when it becomes plural.

Here are some other words that use the zero plural:

* sheep

* deer

* series

* species

While it might seem odd, the zero plural for "bison" is actually a very old form. It's a relic of the ancient Germanic language that has been preserved in English.