diff --git a/src/command.cpp b/src/command.cpp
index eb992a2d2d..ccea6821d2 100644
--- a/src/command.cpp
+++ b/src/command.cpp
@@ -29,7 +29,7 @@
 
 #include "table/strings.h"
 
-StringID _error_message;
+StringID _error_message; ///< Global error message. @see CommandCost::SetGlobalErrorMessage()
 
 CommandProc CmdBuildRailroadTrack;
 CommandProc CmdRemoveRailroadTrack;
@@ -192,7 +192,7 @@ CommandProc CmdSetTimetableStart;
  * The master command table
  *
  * This table contains all possible CommandProc functions with
- * the flags which belongs to it. The indizes are the same
+ * the flags which belongs to it. The indices are the same
  * as the value from the CMD_* enums.
  */
 static const Command _command_proc_table[] = {
@@ -472,8 +472,8 @@ bool DoCommandP(const CommandContainer *container, bool my_cmd)
 /*!
  * Toplevel network safe docommand function for the current company. Must not be called recursively.
  * The callback is called when the command succeeded or failed. The parameters
- * tile, p1 and p2 are from the #CommandProc function. The paramater cmd is the command to execute.
- * The parameter my_cmd is used to indicate if the command is from a company or the server.
+ * \a tile, \a p1, and \a p2 are from the #CommandProc function. The parameter \a cmd is the command to execute.
+ * The parameter \a my_cmd is used to indicate if the command is from a company or the server.
  *
  * @param tile The tile to perform a command on (see #CommandProc)
  * @param p1 Additional data for the command (see #CommandProc)
@@ -482,7 +482,7 @@ bool DoCommandP(const CommandContainer *container, bool my_cmd)
  * @param callback A callback function to call after the command is finished
  * @param text The text to pass
  * @param my_cmd indicator if the command is from a company or server (to display error messages for a user)
- * @return true if the command succeeded, else false
+ * @return \c true if the command succeeded, else \c false.
  */
 bool DoCommandP(TileIndex tile, uint32 p1, uint32 p2, uint32 cmd, CommandCallback *callback, const char *text, bool my_cmd)
 {
diff --git a/src/command_type.h b/src/command_type.h
index fb71eac27c..37b52a94ce 100644
--- a/src/command_type.h
+++ b/src/command_type.h
@@ -91,6 +91,7 @@ public:
 
 	/**
 	 * Sets the global error message *if* this class has one.
+	 * @see _error_message
 	 */
 	FORCEINLINE void SetGlobalErrorMessage() const
 	{
@@ -99,8 +100,8 @@ public:
 	}
 
 	/**
-	 * Makes this CommandCost behave like an error command.
-	 * @param mesasge the error message.
+	 * Makes this #CommandCost behave like an error command.
+	 * @param message The error message.
 	 */
 	void MakeError(StringID message)
 	{
diff --git a/src/company_cmd.cpp b/src/company_cmd.cpp
index 39a889e5e7..ba52c61ebd 100644
--- a/src/company_cmd.cpp
+++ b/src/company_cmd.cpp
@@ -159,6 +159,11 @@ void InvalidateCompanyWindows(const Company *company)
 	SetWindowDirty(WC_FINANCES, cid);
 }
 
+/**
+ * Verify whether the company can pay the bill.
+ * @param cost [inout] Money to pay, is changed to an error if the company does not have enough money.
+ * @return Function returns \c true if the company has enough money, else it returns \c false.
+ */
 bool CheckCompanyHasMoney(CommandCost &cost)
 {
 	if (cost.GetCost() > 0) {
diff --git a/src/rail.h b/src/rail.h
index ebb9b0917e..3f401cd371 100644
--- a/src/rail.h
+++ b/src/rail.h
@@ -31,6 +31,7 @@ DECLARE_ENUM_AS_BIT_SET(RailTypeFlags);
 
 struct SpriteGroup;
 
+/** Sprite groups for a railtype. */
 enum RailTypeSpriteGroup {
 	RTSG_CURSORS,     ///< Cursor and toolbar icon images
 	RTSG_OVERLAY,     ///< Images for overlaying track
diff --git a/src/rail_cmd.cpp b/src/rail_cmd.cpp
index bce6732dae..4f020f4f05 100644
--- a/src/rail_cmd.cpp
+++ b/src/rail_cmd.cpp
@@ -727,7 +727,7 @@ static CommandCost ValidateAutoDrag(Trackdir *trackdir, TileIndex start, TileInd
 	return CommandCost();
 }
 
-/** Build a stretch of railroad tracks.
+/** Build or remove a stretch of railroad tracks.
  * @param tile start tile of drag
  * @param flags operation to perform
  * @param p1 end tile of drag
diff --git a/src/tree_map.h b/src/tree_map.h
index 05315ca253..18966da825 100644
--- a/src/tree_map.h
+++ b/src/tree_map.h
@@ -60,7 +60,7 @@ enum TreeGround {
 	TREE_GROUND_ROUGH       = 1, ///< some rough tile
 	TREE_GROUND_SNOW_DESERT = 2, ///< a desert or snow tile, depend on landscape
 	TREE_GROUND_SHORE       = 3, ///< shore
-	TREE_GROUND_ROUGH_SNOW  = 4, ///< a snow tile that is rough underneed
+	TREE_GROUND_ROUGH_SNOW  = 4, ///< A snow tile that is rough underneath.
 };