diff --git a/theory.en.md b/theory.en.md
index d9afa97..27711d5 100644
--- a/theory.en.md
+++ b/theory.en.md
@@ -2,7 +2,7 @@
 
 Space, objects.
 Is a discrete space, whose cells have sites (syn: vessels, quivers, slots, locations, space holders) directed towards the neighboring cells. These sites may contain zero, one or several arrows that can be stacked and directed towards the same neighboring cell. Any distribution of arrows in the sites is a directed multigraph. It defines a state of the space.
-The cell is the smallest unit of space. All cells are similar. All have the same number of sites. Each cell can have at most as many sites as there are other cells in space. The cells have no site directed towards themselves.
+The cell is the smallest unit of space. All cells are similar. All have the same number of sites. Each cell can have at most as many sites as there are other cells in space. The site zero is directed toward the cell itself.
 Each cell designated by an arrow can itself contain zero, one or several arrows.
 
 An object is an isolated connex part of this graph. Each state space, unless the space is empty or saturated, describes at least one object. According to the number of dimensions of the space, objects of any shape can be drawn: monomers, polymers, strings, knots, surfaces, volumes, cavities, fluids, basic machines, etc ... They can be combined in the same space to describe situations.