In a many-to-one declaration, the hibernate attribute "cascading" may be set to "persist", "save-update", "merge", among others. My question is, what is the difference between the first two? Is there a reason why "persist" is not available in NHibernate?
Also, is there a reason why the attribute "lazy" is not available in NHibernate?

I guess "persist" would be equivalent to "cascade on save only". It's not available because I haven't yet got to it :)

NHibernate has "lazy" for classes and collections, not for individual properties, since implementing it for individual properties would require bytecode manipulation.