diff --git a/opalmap.asciidoc b/opalmap.asciidoc
index e0f36c3e9e3a21ba25844a260b4101744ee45973..51ae3d80fbea74064c4f8b830f0e262e499ecde1 100644
--- a/opalmap.asciidoc
+++ b/opalmap.asciidoc
@@ -35,9 +35,9 @@ PX::
 (Where latexmath:[p_x] is the momentum of the particle and latexmath:[P_0] is the momentum of the reference particle)
 
 Y::
-  Horizontal position latexmath:[y] of a particle relative to the reference particle [m].
+  Vertical position latexmath:[y] of a particle relative to the reference particle [m].
 PY::
-  latexmath:[\frac{p_y}{P_0}] Normalized horizontal canonical momentum [1].
+  latexmath:[\frac{p_y}{P_0}] Normalized Vertical canonical momentum [1].
 Z::
   Longitudinal position latexmath:[z] of a particle relative to the reference particle [m].
 DELTA::
@@ -261,4 +261,4 @@ The first number describes the coefficient and the following 6 the variables of
 anchor:bib.berz1999_opalmap[[{counter:bib-cnt}\]]
 <<bib.berz1999_opalmap>> Martin Berz. Modern map methods in particle beam physics. eng. ISBN: 978-0-12-014750-2. San Diego: Academic Press, 1999.
 
-// EOF
\ No newline at end of file
+// EOF