so i ran into some snags today and was looking to clarify some things.
so, first, reach, is someone infront of me considered 5 feet away? this question comes up for a few reasons, this particular time was over obscuring mist. is someone infront of me considered 5 feet away (20% concealment)? and is someone with one square between us 10 feet away (50% concealment)?
Rules Compendium (since it has better pictures in an easier to find location) pg 18
Threatened squares
If you're considered armed, you threaten all squares into which you can make a melee attack, even when it isn't you turn. That usually means everything in all squares adjacent to your space, including diagonally.
Reach
Most creatures of Medium or smaller size have a reach of only 5 feet. This means that they can make melee attacks only against creatures up to 5 feet (1 square) away.
So any square adjacent to the one the PC is in is considered "5 feet away" - the next square is 10 ft and so on.
This is where mats come in handy to visualize such things.