diff --git a/bib/glossaries/symbols/other.bib b/bib/glossaries/symbols/other.bib
index 83eb149..538ab06 100644
--- a/bib/glossaries/symbols/other.bib
+++ b/bib/glossaries/symbols/other.bib
@@ -1,5 +1,10 @@
-% Math operators
-
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% Math Operators:
+% REQUIRED for the built-in macros
+% to work (\deriv, \vect etc.)!
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 @entry{derivative,
     name={\derivativefmt{\symbolplaceholder}},
     description={infinitesimal change in \symbolplaceholder},
@@ -17,6 +22,26 @@ @entry{difference
 }
 @entry{flow,
     name={\flowfmt{\symbolplaceholder}},
-    description={\symbolplaceholder{} as a flowing quantity},
+    description={\symbolplaceholder{} as a flow quantity},
     unit={\si{\symbolplaceholder\per\second}},
 }
+@entry{nabla,
+    name={\nablaoperatorfmt{\symbolplaceholder}},
+    description={Vector of partial derivatives (Nabla operator) of \symbolplaceholder},
+    unit={--},
+}
+@entry{mean,
+    name={\meanfmt{\symbolplaceholder}},
+    description={Arithmetic mean of \symbolplaceholder{}},
+    unit={\symbolplaceholder},
+}
+@entry{logmean,
+    name={\logmeanfmt{\symbolplaceholder}},
+    description={Logarithmic mean of \symbolplaceholder{}},
+    unit={\symbolplaceholder},
+}
+@entry{vector,
+    name={\ensuremath{\vectfmt{x}}},
+    description={Vector},
+    unit={--},
+}
diff --git a/bib/glossaries/symbols/roman.bib b/bib/glossaries/symbols/roman.bib
index 68149ae..b4f430e 100644
--- a/bib/glossaries/symbols/roman.bib
+++ b/bib/glossaries/symbols/roman.bib
@@ -79,6 +79,7 @@ @symbol{heat_capacity
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 % Coordinates etc.
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% REQUIRED for built-in \posderiv to work:
 @symbol{first_cart_coord,
     name={\ensuremath{x}},
     description={First Cartesian coordinate (length)},
@@ -104,6 +105,12 @@ @symbol{area
     description={Area},
     unit={\si{\meter\squared}},
 }
+% REQUIRED for built-in \timederiv to work:
+@symbol{time,
+    name={\ensuremath{t}},
+    description={Time},
+    unit={\si{\second}},
+}
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 % Electrical
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
diff --git a/cookbook.cls b/cookbook.cls
index a311b23..8e36532 100644
--- a/cookbook.cls
+++ b/cookbook.cls
@@ -2315,20 +2315,20 @@
 
 % Time derivative
 \newcommand*{\timederiv}[2][]{%
-    \fracderiv[#1]{#2}{\gls{sym.zeit}}%
+    \fracderiv[#1]{#2}{\gls{sym.time}}%
 }%
 % Partial Time derivative
 \WithSuffix\newcommand\timederiv*[2][]{%
-    \fracderiv*[#1]{#2}{\gls{sym.zeit}}%
+    \fracderiv*[#1]{#2}{\gls{sym.time}}%
 }
 
 % Positional derivative
 \newcommand*{\posderiv}[2][]{%
-    \fracderiv[#1]{#2}{\gls{sym.x}}%
+    \fracderiv[#1]{#2}{\gls{sym.first_cart_coord}}%
 }
 % Partial Positional derivative
 \WithSuffix\newcommand\posderiv*[2][]{%
-    \fracderiv*[#1]{#2}{\gls{sym.x}}%
+    \fracderiv*[#1]{#2}{\gls{sym.first_cart_coord}}%
 }
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%