What options are open to a woman whose husband marries someone else while still married to her? Is that bigamy?

Yes, marrying again during the lifetime of one's wife or husband is known as bigamy. It is a criminal offence, punishable with imprisonment and fine. A bigamous marriage is void, a complete nullity. If a woman has prima facie evidence that she is lawfully married to a man who is about to or has remarried, she can register a criminal complaint and the police are expected to stop him from getting remarried. If a wife learns that her husband is going to marry again she can get an injunction from the court forbidding the marriage before it occurs. After it has taken place, a wife can ask the court for a "declaration" that the second or bigamous marriage is null and void. Proving bigamy, however, is not easy. The complainant wife has to prove that both the marriages, her own as well as the second bigamous one, have been performed properly according to the appropriate ceremonies. Most prosecutions for bigamy fail because the complainant does not have the proof of the bigamous marriage. The accused husband can usually successfully claim against all efforts to prove the contrary that essential parts of the ceremony were never carried out and escape punishment.