What does "familiar" mean in the Sending spell?

Question

The Sending spell states that:

You send a short message of twenty-five words or less to a creature with which you are familiar. The creature hears the message in its mind, recognizes you as the sender if it knows you, and can answer in a like manner immediately. (PHB, p. 274.)

So what counts as 'familiar'? I initially assumed that the intent was somebody you personally knew, perhaps by name, but the inclusion of the phrase "if it knows you" would suggest that the target of the spell need not have any idea of your existence.

Is passing somebody on the street enough? Seeing them from a distance? Being introduced once? How about having them described to you by somebody who does know them?

I'm wondering, among other things, what implications this has for magical spam mail...

Answer 1

Familiar is described a few different ways in the PHB, but the context seems generally the same down the board. I will provide a few (not all) quotes if I can find them.

Clairvoyance: "...in a location familiar to you (A place you have visited or seen before)..." -PHB pg 222

The entry for Scrying on PHB pg. 273 breaks down knowledge of a place or creature pretty well. Familiar: You know the target well

It boils down to there not being a written definition of what is or is not 'familiar' to your character. This means you may have to deliberate with your DM if you are uncertain. Are you familiar with your adventuring group? More than likely. Are you familiar with the Orc who carried you over the cliff into the ocean a few weeks ago? You might think so. Are you familiar with the necromancer you've only heard stories about and can pinpoint its exact location? No.

If I would have to make a ruling about familiarity, I would refer to the Scrying entry.

Answer 2

Familiarity is assymetric

It is very possible for the caster to be closely familiar with the target, yet at the same time the target does not know the caster even exists. Think of real-world superfans that know every little detail about the star they adore, yet the star is entirely oblivious to their existence.

In a fantasy setting, where we are dealing with an arcane caster capable of Sending, they could easily have access to Find Familiar, Invisibility, or even Clairvoyance, to spy on the subject of Sending. Normal investigations, talking to neighbors and business associates would also work.

How familiar does the caster have to be with the subject?

As has been touched upon in the other answers already, there are a number of definitions of the term "familiar" in other contexts:

• Scrying: you know the target well exceeding "firsthand" you have met the target

• Locate Creature: known to you

• Clairvoyance: visited or seen before

• Locate Object: known to you, as long as you have seen it up close -- within 30 feet -- at least once

The two major readings would be that it means (a) you know the target well, better than from a single casual interaction and (b) you have met or seen the target at least once up close.

With several offered, it's up to the DM which interpretation they use. That the target may not know the caster does not influence the decision.

Answer 3

There are a few ways to determine how familiar "familiar" is.
Dream works similarly but uses different wording, targeting "a creature you know of" thus, familiar is more familiar than knowing the creature, otherwise, they would use the same wording. Thus, you have to have to at least know, what they look like, and what they sound like, because that's one step above knowing about someone.

Scrying uses the word "familiar" explicitly to mean "you know the target well" and it is more familiar than firsthand knowledge, which is "you have met the target".
This suggests at minimum, from the fact that it is more than having met, you have had at least a conversation that goes beyond introductions.

But Clairvoyance describes familiar as having seen a place before. People aren't places, but that's a lot lighter than being friends.

I'd probably put it at first-hand knowledge the same as clairvoyance. You can't send a sending to the king you never met. I'd prefer it be less harsh than scrying, because scrying you lose out on a -5 to save if you aren't familiar, but with sending it fails. But that's just generosity.

Familiarity is described by sending. More than having met them, knowing them well. It's also described in clairvoyance, as "having seen before."

Either way, second-hand knowledge certainly isn't enough, as we see from dream: when second-hand knowledge is the prerequisite, it doesn't use the word 'familiar.'