How many words does koko know?

Koko is a Western lowland gorilla who has been the subject of a long-term study of animal language. Koko understands more than 1,000 signs of American Sign Language (ASL) and is able to use them to communicate with humans. She is also able to understand spoken English and can even produce some simple words. Koko's story has been featured in numerous documentaries and books, and she has become a celebrated example of animal intelligence and communication.