What Prefix for all that is 3 letters?

There isn't a single, universally accepted prefix for "all that is" that is only three letters long.

Here are some options that come close:

* Pan-: This prefix means "all" or "everything" and can be used to form words like "panoramic" or "pandemic". However, it's not specific to "all that is" in a philosophical sense.

* Tot-: While "tot" can mean "all" in some contexts, it's not a standard prefix and would be considered quite informal.

For a more specific philosophical meaning, you might consider using a phrase like "all-encompassing" or "omni-" (which means "all" or "everything") to describe the concept of "all that is."