Types of open relationships :

• Some relationships place strict restrictions on partners (e.g. polyfidelity); such relationships are polyamorous, but not open.
• Some relationships permit sex outside the primary relationship, but not love (e.g. swinging); such relationships are sexually non-monogamous but not polyamorous or open.
• Some polyamorists consider 'polyamory' to be their philosophical orientation — they believe themselves capable and desirous of multiple loves — whereas 'open relationship' is used as a logistical description: that is, it is how their polyamory is expressed or implemented. They would say of themselves, for instance, "I am polyamorous; my primary partner and I have an open relationship (with the following ground rules)...."

The "open" in "open relationship" usually refers to the sexual aspect of a non-closed relationship, whereas "polyamory" refers to the extension of a relationship by allowing bonds to form (which may be sexual or otherwise) as additional long term relationships.

Those in "open relationships" might refer to themselves as "O.R.F.F.s" (open relationship friends forever), a take on the more common acronym "B.F.F." which refers to "best friends forever."