What is Chicken ?
Chicken is (noun) 1. a young hen Chickens were running everywhere in the farmyard. (NOTE: The plural is chickens.) 2. meat from a hen We’re having roast chicken for lunch. Would you like another slice of chicken? We bought some chicken sandwiches for lunch. (NOTE: no plural: some chicken; a piece of chicken; a slice of chicken)
source: Easier English, Student Dictionary Upper Intermediate Level