The word "chicken" refers to a single individual of the species, but when there is more than one, we use the plural form "chickens". It is important to remember that adding an "s" to the end of "chicken" creates the plural form, just like many other nouns in English. So, if you are referring to multiple chickens, you would say "chickens".
For example, if you have a farm with several chickens, you would say "I have many chickens on my farm". Similarly, if you are talking about a meal with multiple chicken pieces, you would say "We ordered three fried chickens for dinner".
The plural form "chickens" is used to accurately denote more than one individual in English. It is a simple and commonly used rule in the English language.