Returns an association mapping each word to its number of occurrences.
WordCounts["string"]
WordCounts["string", n]
WordCounts[{"string1", "string2", …}, …]
WordCounts["the cat and the dog"]
→ <|the -> 2, dog -> 1, and -> 1, cat -> 1|>WordCounts["one fish, two fish, red fish"]
→ <|fish -> 3, red -> 1, two -> 1, one -> 1|>WordCounts["a b a b a", 2]
→ <|{b, a} -> 2, {a, b} -> 2|>