diff --git a/src/CLASS2/dihedral_class2.h b/src/CLASS2/dihedral_class2.h
index 96a04ab0db..cc1f13674e 100644
--- a/src/CLASS2/dihedral_class2.h
+++ b/src/CLASS2/dihedral_class2.h
@@ -59,7 +59,8 @@ class DihedralClass2 : public Dihedral {
 
 W: Dihedral problem: %d %ld %d %d %d %d
 
-UNDOCUMENTED
+Conformation of the 4 listed dihedral atoms is extreme; you may want
+to check your simulation geometry. :dd
 
 E: Invalid coeffs for this dihedral style
 
diff --git a/src/CLASS2/improper_class2.h b/src/CLASS2/improper_class2.h
index 93be87e9c6..58508fda14 100644
--- a/src/CLASS2/improper_class2.h
+++ b/src/CLASS2/improper_class2.h
@@ -54,7 +54,8 @@ class ImproperClass2 : public Improper {
 
 W: Improper problem: %d %ld %d %d %d %d
 
-UNDOCUMENTED
+Conformation of the 4 listed improper atoms is extreme; you may want
+to check your simulation geometry. :dd
 
 E: Incorrect args for improper coefficients
 
diff --git a/src/MOLECULE/bond_fene.h b/src/MOLECULE/bond_fene.h
index ff6112d84c..88f50952c4 100644
--- a/src/MOLECULE/bond_fene.h
+++ b/src/MOLECULE/bond_fene.h
@@ -53,7 +53,8 @@ class BondFENE : public Bond {
 
 W: FENE bond too long: %ld %d %d %g
 
-UNDOCUMENTED
+A FENE bond has stretched dangerously far.  It's interaction strength
+will be truncated to attempt to prevent the bond from blowing up. :dd
 
 E: Bad FENE bond
 
@@ -70,6 +71,7 @@ Most FENE models need this setting for the special_bonds command.
 
 W: FENE bond too long: %ld %g
 
-UNDOCUMENTED
+A FENE bond has stretched dangerously far.  It's interaction strength
+will be truncated to attempt to prevent the bond from blowing up. :dd
 
 */
diff --git a/src/MOLECULE/bond_fene_expand.h b/src/MOLECULE/bond_fene_expand.h
index 4c51067380..bae8a73273 100644
--- a/src/MOLECULE/bond_fene_expand.h
+++ b/src/MOLECULE/bond_fene_expand.h
@@ -53,7 +53,8 @@ class BondFENEExpand : public Bond {
 
 W: FENE bond too long: %ld %d %d %g
 
-UNDOCUMENTED
+A FENE bond has stretched dangerously far.  It's interaction strength
+will be truncated to attempt to prevent the bond from blowing up. :dd
 
 E: Bad FENE bond
 
@@ -70,6 +71,7 @@ Most FENE models need this setting for the special_bonds command.
 
 W: FENE bond too long: %ld %g
 
-UNDOCUMENTED
+A FENE bond has stretched dangerously far.  It's interaction strength
+will be truncated to attempt to prevent the bond from blowing up. :dd
 
 */
diff --git a/src/MOLECULE/dihedral_charmm.h b/src/MOLECULE/dihedral_charmm.h
index 3055b27035..44a93357f5 100644
--- a/src/MOLECULE/dihedral_charmm.h
+++ b/src/MOLECULE/dihedral_charmm.h
@@ -53,7 +53,8 @@ class DihedralCharmm : public Dihedral {
 
 W: Dihedral problem: %d %ld %d %d %d %d
 
-UNDOCUMENTED
+Conformation of the 4 listed dihedral atoms is extreme; you may want
+to check your simulation geometry. :dd
 
 E: Incorrect args for dihedral coefficients
 
diff --git a/src/MOLECULE/dihedral_harmonic.h b/src/MOLECULE/dihedral_harmonic.h
index 3952442053..ce78bcd992 100644
--- a/src/MOLECULE/dihedral_harmonic.h
+++ b/src/MOLECULE/dihedral_harmonic.h
@@ -50,7 +50,8 @@ class DihedralHarmonic : public Dihedral {
 
 W: Dihedral problem: %d %ld %d %d %d %d
 
-UNDOCUMENTED
+Conformation of the 4 listed dihedral atoms is extreme; you may want
+to check your simulation geometry. :dd
 
 E: Incorrect args for dihedral coefficients
 
diff --git a/src/MOLECULE/dihedral_helix.h b/src/MOLECULE/dihedral_helix.h
index b604f056d4..6f254ad948 100644
--- a/src/MOLECULE/dihedral_helix.h
+++ b/src/MOLECULE/dihedral_helix.h
@@ -49,7 +49,8 @@ class DihedralHelix : public Dihedral {
 
 W: Dihedral problem: %d %ld %d %d %d %d
 
-UNDOCUMENTED
+Conformation of the 4 listed dihedral atoms is extreme; you may want
+to check your simulation geometry. :dd
 
 E: Incorrect args for dihedral coefficients
 
diff --git a/src/MOLECULE/dihedral_multi_harmonic.h b/src/MOLECULE/dihedral_multi_harmonic.h
index e06fd6ad70..8ba96dc0c9 100644
--- a/src/MOLECULE/dihedral_multi_harmonic.h
+++ b/src/MOLECULE/dihedral_multi_harmonic.h
@@ -49,7 +49,8 @@ class DihedralMultiHarmonic : public Dihedral {
 
 W: Dihedral problem: %d %ld %d %d %d %d
 
-UNDOCUMENTED
+Conformation of the 4 listed dihedral atoms is extreme; you may want
+to check your simulation geometry. :dd
 
 E: Incorrect args for dihedral coefficients
 
diff --git a/src/MOLECULE/dihedral_opls.h b/src/MOLECULE/dihedral_opls.h
index d72e589f98..887507324e 100644
--- a/src/MOLECULE/dihedral_opls.h
+++ b/src/MOLECULE/dihedral_opls.h
@@ -49,7 +49,8 @@ class DihedralOPLS : public Dihedral {
 
 W: Dihedral problem: %d %ld %d %d %d %d
 
-UNDOCUMENTED
+Conformation of the 4 listed dihedral atoms is extreme; you may want
+to check your simulation geometry. :dd
 
 E: Incorrect args for dihedral coefficients
 
diff --git a/src/MOLECULE/improper_cvff.h b/src/MOLECULE/improper_cvff.h
index b081d4d09d..410522952f 100644
--- a/src/MOLECULE/improper_cvff.h
+++ b/src/MOLECULE/improper_cvff.h
@@ -50,7 +50,8 @@ class ImproperCvff : public Improper {
 
 W: Improper problem: %d %ld %d %d %d %d
 
-UNDOCUMENTED
+Conformation of the 4 listed improper atoms is extreme; you may want
+to check your simulation geometry. :dd
 
 E: Incorrect args for improper coefficients
 
diff --git a/src/MOLECULE/improper_harmonic.h b/src/MOLECULE/improper_harmonic.h
index aa6642b9f4..5e5c0bf22a 100644
--- a/src/MOLECULE/improper_harmonic.h
+++ b/src/MOLECULE/improper_harmonic.h
@@ -49,7 +49,8 @@ class ImproperHarmonic : public Improper {
 
 W: Improper problem: %d %ld %d %d %d %d
 
-UNDOCUMENTED
+Conformation of the 4 listed improper atoms is extreme; you may want
+to check your simulation geometry. :dd
 
 E: Incorrect args for improper coefficients
 
diff --git a/src/MOLECULE/improper_umbrella.h b/src/MOLECULE/improper_umbrella.h
index fb549f6a86..6a566d606d 100644
--- a/src/MOLECULE/improper_umbrella.h
+++ b/src/MOLECULE/improper_umbrella.h
@@ -49,7 +49,8 @@ class ImproperUmbrella : public Improper {
 
 W: Improper problem: %d %ld %d %d %d %d
 
-UNDOCUMENTED
+Conformation of the 4 listed improper atoms is extreme; you may want
+to check your simulation geometry. :dd
 
 E: Incorrect args for improper coefficients
 
diff --git a/src/SHOCK/fix_append_atoms.cpp b/src/SHOCK/fix_append_atoms.cpp
index 39e7a7c091..4a87d616f6 100644
--- a/src/SHOCK/fix_append_atoms.cpp
+++ b/src/SHOCK/fix_append_atoms.cpp
@@ -394,7 +394,7 @@ void FixAppendAtoms::pre_exchange()
 	nbasis = domain->lattice->nbasis;
 	basistype = new int[nbasis];
 	for (int i = 0; i < nbasis; i++) basistype[i] = 1;
-      } else error->all(FLERR,"must define lattice to append_atoms");
+      } else error->all(FLERR,"Must define lattice to append_atoms");
 
       double bboxlo[3],bboxhi[3];
 
diff --git a/src/SHOCK/fix_append_atoms.h b/src/SHOCK/fix_append_atoms.h
index 7ae2da37c0..cdd9428405 100644
--- a/src/SHOCK/fix_append_atoms.h
+++ b/src/SHOCK/fix_append_atoms.h
@@ -95,7 +95,11 @@ E: Fix ID for fix ave/spatial does not exist
 
 Self-explanatory.
 
-E: must define lattice to append_atoms
+E: Must define lattice to append_atoms
+
+UNDOCUMENTED
+
+U: must define lattice to append_atoms
 
 UNDOCUMENTED
 
diff --git a/src/dump_cfg.h b/src/dump_cfg.h
index 858e0697e6..0f3c35e33b 100755
--- a/src/dump_cfg.h
+++ b/src/dump_cfg.h
@@ -50,7 +50,7 @@ class DumpCFG : public DumpCustom {
 
 E: Dump cfg arguments must start with 'id type xs ys zs' or 'id type xsu ysu zsu'
 
-UNDOCUMENTED
+This is a requirement of the CFG output format. :dd
 
 E: Dump cfg arguments can not mix xs|ys|zs with xsu|ysu|zsu
 
diff --git a/src/fix_shake.h b/src/fix_shake.h
index fdfe23d3e7..a0727b7cbc 100644
--- a/src/fix_shake.h
+++ b/src/fix_shake.h
@@ -179,15 +179,21 @@ types for the 2 bonds in the angle.
 
 E: Shake atoms %d %d missing on proc %d at step %ld
 
-UNDOCUMENTED
+The 2 atoms in a single shake cluster specified by the fix shake
+command are not all accessible to a processor.  This probably means
+an atom has moved too far. :dd
 
 E: Shake atoms %d %d %d missing on proc %d at step %ld
 
-UNDOCUMENTED
+The 3 atoms in a single shake cluster specified by the fix shake
+command are not all accessible to a processor.  This probably means
+an atom has moved too far. :dd
 
 E: Shake atoms %d %d %d %d missing on proc %d at step %ld
 
-UNDOCUMENTED
+The 4 atoms in a single shake cluster specified by the fix shake
+command are not all accessible to a processor.  This probably means
+an atom has moved too far. :dd
 
 E: Did not find fix shake partner info
 
diff --git a/src/memory.h b/src/memory.h
index e47dad97c3..0073be189f 100644
--- a/src/memory.h
+++ b/src/memory.h
@@ -484,11 +484,13 @@ class Memory : protected Pointers {
 
 E: Failed to allocate %ld bytes for array %s
 
-UNDOCUMENTED
+Your LAMMPS simulation has run out of memory.  You need to run a
+smaller simulation or on more processors. :dd
 
 E: Failed to reallocate %ld bytes for array %s
 
-UNDOCUMENTED
+Your LAMMPS simulation has run out of memory.  You need to run a
+smaller simulation or on more processors. :dd
 
 E: Cannot create/grow a vector/array of pointers for %s
 
diff --git a/src/neigh_bond.h b/src/neigh_bond.h
index 351810f5a1..c698aad115 100644
--- a/src/neigh_bond.h
+++ b/src/neigh_bond.h
@@ -15,18 +15,30 @@
 
 E: Bond atoms %d %d missing on proc %d at step %ld
 
-UNDOCUMENTED
+One or both of 2 atoms needed to compute a particular bond are
+missing on this processor.  Typically this is because the pairwise
+cutoff is set too short or the bond has blown apart and an atom is
+too far away. :dd
 
 E: Angle atoms %d %d %d missing on proc %d at step %ld
 
-UNDOCUMENTED
+One or more of 3 atoms needed to compute a particular angle are
+missing on this processor.  Typically this is because the pairwise
+cutoff is set too short or the angle has blown apart and an atom is
+too far away. :dd
 
 E: Dihedral atoms %d %d %d %d missing on proc %d at step %ld
 
-UNDOCUMENTED
+One or more of 4 atoms needed to compute a particular dihedral are
+missing on this processor.  Typically this is because the pairwise
+cutoff is set too short or the dihedral has blown apart and an atom is
+too far away. :dd
 
 E: Improper atoms %d %d %d %d missing on proc %d at step %ld
 
-UNDOCUMENTED
+One or more of 4 atoms needed to compute a particular improper are
+missing on this processor.  Typically this is because the pairwise
+cutoff is set too short or the improper has blown apart and an atom is
+too far away. :dd
 
 */