Intensive Outpatient Treatment (also known as IOP for Intensive Outpatient Program) is a primary treatment program recommended in some circumstances by a clinical and medical assessment. IOP may be recommended for those who do not need medically-supervised detox.
The genitive is the case (or function) of an inflected form of a noun or pronoun showing ownership, measurement, association, or source. Adjective: genitival. The suffix -'s on nouns is a marker of genitive case in English. Genitive case can also be indicated by an of phrase after a noun.
Their most often use is non-finite verbs. In traditional descriptions of English, the infinitive is the basic dictionary form of a verb when used non-finitely, with or without the particle to. Thus to go is an infinitive, as is go in a sentence like I must go there (but not in I go there, where it is a finite verb).