Unforgivable omission for a tennis forum:Polyglot- person who knows/can use several languages.
Polymath- a person with an extensive range of knowledge, a "renaissance type".
Polygamy- the practice of a male having more than one wife.
Polyandry- the practice of a female having more than one husband.
Polyamorous- refers to a person who has multiple, serious, romantic relationships at the same time (not just casual encounters).
Polymorphic- occurring in various forms, variations.
Polyphonic- in music, a style of harmonizing many parts into a singular melody.
Polyphemus- In Greek mythology, a cyclops, son of Poseidon.