@Essie13 asked a good question. (That’s one of the hot things she does.)
What makes a partner different from a friend?
Some people won’t care about that. They don’t like or use labels for relationships, or have wide definitions rather than taxonomies. That can be a comfortable way to live.
For those who do distinguish, though, the line between friendship (with or without benefits) and partnership can be an important one in establishing boundaries for behavior, when planning future activities, in setting goals or aspirations for a relationship… and so much more.
So what makes a partner?
Is it sex? No, because I can (and do) have romantic relationships with partners in which there is no sex. And I can and do have sex with people I enjoy and care about, but do not consider partners.
Is it frequency of visitation? No, because I have partners I see two or three times a year, and friends I see far more often.
For me, at least, partnership occurs when a romantic relationship exists–a non-obligatory exchange of Big-L ”I love you”; when there is commitment to developing and expanding the relationship; and when you include that person in your life planning. Decisions about where to live, for example, take that person into account.
One clear sign of partnership is the change from finding time in the schedule to be together to moving other things to create that time.
And a partnership is mutual. One may never be certain whether someone we call a friend feels the same way about us; it’s a term that covers a range of relationships and emotions. Partnerships, though, perhaps because they are defined at base by mutual support and regard, exist only when there is common and avowed commitment.
Friends can go very different directions and eventually wind up at the same place. Partners tend to travel together.
Beyond that, as Potter Stewart said of pornography: “I can’t define it, but I know it when I see it.” Or, more likely, feel it.