My beloved Basset Hound knew a lot of English words, as long as they start with "cookie." Well, turns out that she's a bit far behind this dog, a border collie in Spartanburg, South Carolina, named Chaser, who has the largest vocabulary of any known dog:
[Psychologist John W. Pilley] bought Chaser as a puppy in 2004 from a local border collie breeder and started to train her for four to five hours a day. He would show her an object, say its name up to 40 times, then hide it and ask her to find it, while repeating the name all the time. She was taught one or two new names a day, with monthly revisions and reinforcement for any names she had forgotten.
He did this day in day out for years until Chaser knows the names of 1,022 items: Link (Photo: Cass Sapir/Nova scienceNOW)