Term: Radius

A radius, sometimes called an emanation or a burst, is an area around a space or unit. The radial area extends out to a specified number of ft in all directions, including the third dimension.

The stated radius does not include the space the unit is taking up (meaning a radius of 5 ft is, in reality, 10 ft if measuring from the center of where it starts, but 5 ft if measuring from the edge). When the radius comes from a creature, as with an Aura, it includes the creature's space (i.e. meaning a creature that is Large or Larger has a larger radius).

For instance, a Torch has a radius/emanation of 15 ft of bright light, lighting up a 5 ft / 1.5m square area and ~15 ft / ~5 m radius around it (and does not grow in size, if held by a Large creature). Unless the text states otherwise, the creature creating a radius effect chooses whether the creature at its center is affected.

For full rules on Areas of Effect, go to Rule: Areas of Effect.