An Annulment means that the marriage was void from the very beginning because there was something wrong with the spouses or something happened after the marriage to make one spouse legally incapable. This means there is a very narrow set of circumstances in which an annulment can take place:
1. If either of the spouses is incurably incapable of having sexual relations;
2. If one of the spouses is under the age of 18 and wants an annulment;
3. If either of the spouses becomes incurably insane for five years or more (note that the sane spouse may be required to support the insane spouse); or
4. If either spouse consented to the marriage as a result of force, duress or certain instances of fraud.
And, certain marriages are not recognized – such as those between relatives or those where bigamy has occurred – and may be declared null by the issuance of such a declaration by the court.
A Divorce, on the other hand, would cover the dissolution of most marriages. In New York, the spouse seeking the divorce must either use the new No Fault grounds for divorce (i.e. the marriage is irretrievably broken for more than 6 months) or have grounds for divorce such as abandonment, adultery or cruel and inhuman treatment.
Practically speaking, of course, whether the court grants a divorce, annulment or declaration of nullity, the legal result is the same: the dissolution of the marriage as a matter of public record.