Significant other (SO) is the gender neutral term that is used to describe an individual's intimate relationship with another individual. Generally, the term is used because it does not disclose marital status, sexual orientation, or relationship status.
More About Significant Other (SO)
Significant other is a colloquial expression used in many different countries instead of using spousal reference terms. The term is favored over others because it does not presume a sexual orientation or gender of the individuals involved. It does not assume a marital or relationship status. It is a term used often on social or medical documents. For example, a wedding invitation might express that the individual come with their significant other or medical professionals might explain that the patient's significant other may be present for a medical procedure.