"collision", like in "hash collision"?

What do you mean by "four-space location"? "location in four-dimensional space"? Or "location which is four spaces in size"?

A location in space and time.

Really I only care about latitude, longitude, and date/time, so really it's three-space, but there are occasions when it also uses altitude, so 4-space is properly accurate.

The event could be an Encounter.

The condition could be DOUBLE_OCCUPANCY.

I like "Encounter" a lot. "Coincidence" might work too.

A close encounter, yes. If it were a continuous value, they'd be proximity minima.

Of which kind?

To clarify: This coincidences of four-space location are a good thing, and the point is to help find them. Giving them a natural, catchy name is critical to help people understand that they are desirable.

Thanks to those who have contributed so far - much appreciated. Shame this didn't get more upvotes, attention, and/or more suggestions. <fx: shrug />

You want something more optimistic. I think the correct word in Spanish is "encuentro": (autotranslation) meeting, encounter, match, citation, collision, smash, clash

Looking at the backtranslations, one of the suggestions in Spanish is "reunión": (autotranslation) meeting, reunion, gathering, assembly, collect, party

Depends what the things are. And you didn't say (please clarify?) whether this is a user-facing name, or a name seen only by coders. I'm not meaning to diminish the importance of either, btw.

For people, it could be a meetup, but others have already offered many better suggestions, such as convergences and serendipities, which both sound good. But maybe you want something shorter.

What they do when they get together could also lead to naming ideas. For example, if they connect with each other like modules on the International Space Station, it could be a "dock" event. Your real use case is probably different but you should think about what they do, and what result comes out of their being together, as a source of ideas.

Since you say these coincidences are positive:

- serendipities

- run-ins

- meetings

- fortuities

- hookups

- trysts

- rendezvous

- dates

- picnics

- kisses

- embraces

- touches

- bumps

- blends

. . . inspired by thinking about: lovers, asteroids, colored spotlights. Sometimes a whimsical model helps. :-)

In classic CS, when you have two or more things in one place, that could potentially be a "pigeonhole" situation, no?

If they're not supposed to be in the same place at the same time, potentially 'conflict' (in HTTP 409 sense)

A "CoLocation" or "CoLoc" for short.

Coin a short, memorable term, then use both terms everywhere until your users have been around for a time. As a user gets more experienced on the site, drop the longer term and use the "jargon" term. It's a novel concept, it deserves a neologism.

A synchronicity, a synchronization, a sync. A simultaneity. An overlap. A meeting. A touch. A carom.

If "two of them" are the maximum then I would go with "pair".

tuple collision (in this particular case, quadruple collision if you have 4 slots).

http://en.wikipedia.org/wiki/Tuple

Dalliance.

a convergence?

or maybe... an interaction?

If it's a rare and special event, perhaps entanglement?

From the pigeon hole principle.

Pigeons impersonating love birds?

Pigeon collision?

Pauli violation

how about a pair? Like in memory?

Fusion

Octave

Unison

Marriage