diff --git a/applications/utilities/postProcessing/dataConversion/smapToFoam/smapToFoam.C b/applications/utilities/postProcessing/dataConversion/smapToFoam/smapToFoam.C
index 15627c8a89..b72c538d1f 100644
--- a/applications/utilities/postProcessing/dataConversion/smapToFoam/smapToFoam.C
+++ b/applications/utilities/postProcessing/dataConversion/smapToFoam/smapToFoam.C
@@ -2,7 +2,7 @@
   =========                 |
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     | Website:  https://openfoam.org
-    \\  /    A nd           | Copyright (C) 2011-2018 OpenFOAM Foundation
+    \\  /    A nd           | Copyright (C) 2011-2019 OpenFOAM Foundation
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
 License
@@ -52,7 +52,7 @@ int main(int argc, char *argv[])
     dictionary fieldNameDict;
     forAll(fieldNames, i)
     {
-        fieldNameDict.add(fieldNames[i], word(fieldNames[i]));
+        fieldNameDict.add(word(fieldNames[i]), word(fieldNames[i]));
     }
 
     dictionary nameMap;
diff --git a/src/OpenFOAM/db/dictionary/entry/entryIO.C b/src/OpenFOAM/db/dictionary/entry/entryIO.C
index 72e52ed22f..303c559fe9 100644
--- a/src/OpenFOAM/db/dictionary/entry/entryIO.C
+++ b/src/OpenFOAM/db/dictionary/entry/entryIO.C
@@ -51,27 +51,9 @@ bool Foam::entry::getKeyword(keyType& keyword, token& keywordToken, Istream& is)
     }
     while (keywordToken == token::END_STATEMENT);
 
-    // If the token is a valid keyword set 'keyword' return true...
-    if (keywordToken.isWord())
-    {
-        keyword = keywordToken.wordToken();
-        return true;
-    }
-    else if (keywordToken.isVariable())
-    {
-        keyword = keywordToken.variableToken();
-        return true;
-    }
-    else if (keywordToken.isString())
-    {
-        // Enable wildcards
-        keyword = keywordToken.stringToken();
-        return true;
-    }
-    else
-    {
-        return false;
-    }
+    keyword = keywordToken;
+
+    return !keyword.isUndefined();
 }
 
 
@@ -180,7 +162,7 @@ bool Foam::entry::New(dictionary& parentDict, Istream& is)
         else if
         (
            !disableFunctionEntries
-         && keyword[0] == '$'
+         && keyword.isVariable()
         )                           // ... Substitution entry
         {
             token nextToken(is);
diff --git a/src/OpenFOAM/db/dictionary/functionEntries/negEntry/negEntry.C b/src/OpenFOAM/db/dictionary/functionEntries/negEntry/negEntry.C
index df1db047eb..61417a07db 100644
--- a/src/OpenFOAM/db/dictionary/functionEntries/negEntry/negEntry.C
+++ b/src/OpenFOAM/db/dictionary/functionEntries/negEntry/negEntry.C
@@ -64,17 +64,6 @@ Foam::string Foam::functionEntries::negEntry::negateVariable
     // Read variable name as a word including the '$'
     const variable var(is);
 
-    if (var[0] != '$')
-    {
-        FatalIOErrorInFunction
-        (
-            parentDict
-        )   << "Expected variable name beginning with a '$' but found '"
-            << var << "'" << exit(FatalIOError);
-
-        return string::null;
-    }
-
     // Strip the leading '$' from the variable name
     const string varName = var(1, var.size() - 1);
 
diff --git a/src/OpenFOAM/db/dictionary/primitiveEntry/primitiveEntry.C b/src/OpenFOAM/db/dictionary/primitiveEntry/primitiveEntry.C
index 9646bcc4cf..b06dbe4105 100644
--- a/src/OpenFOAM/db/dictionary/primitiveEntry/primitiveEntry.C
+++ b/src/OpenFOAM/db/dictionary/primitiveEntry/primitiveEntry.C
@@ -41,28 +41,28 @@ void Foam::primitiveEntry::append(const UList<token>& varTokens)
 
 bool Foam::primitiveEntry::expandVariable
 (
-    const string& w,
+    const variable& w,
     const dictionary& dict
 )
 {
     if (w.size() > 2 && w[0] == '$' && w[1] == token::BEGIN_BLOCK)
     {
         // Recursive substitution mode. Replace between {} with expansion.
-        string s(w(2, w.size()-3));
+        string s(w(2, w.size() - 3));
 
         // Substitute dictionary and environment variables. Do not allow
         // empty substitutions.
         stringOps::inplaceExpand(s, dict, true, false);
-        string newW(w);
-        newW.std::string::replace(1, newW.size()-1, s);
+        variable newW(w);
+        newW.std::string::replace(1, newW.size() - 1, s);
 
         return expandVariable(newW, dict);
     }
     else
     {
-        string varName = w(1, w.size()-1);
+        string varName = w(1, w.size() - 1);
 
-        // lookup the variable name in the given dictionary....
+        // Lookup the variable name in the given dictionary....
         // Note: allow wildcards to match? For now disabled since following
         // would expand internalField to wildcard match and not expected
         // internalField:
@@ -84,7 +84,7 @@ bool Foam::primitiveEntry::expandVariable
         }
         else
         {
-            // not in the dictionary - try an environment variable
+            // Not in the dictionary - try an environment variable
             string envStr = getEnv(varName);
 
             if (envStr.empty())
diff --git a/src/OpenFOAM/db/dictionary/primitiveEntry/primitiveEntry.H b/src/OpenFOAM/db/dictionary/primitiveEntry/primitiveEntry.H
index 59904ab631..873c6dda55 100644
--- a/src/OpenFOAM/db/dictionary/primitiveEntry/primitiveEntry.H
+++ b/src/OpenFOAM/db/dictionary/primitiveEntry/primitiveEntry.H
@@ -71,23 +71,13 @@ class primitiveEntry
         void append(const UList<token>&);
 
         //- Append the given token to this entry
-        void append
-        (
-            const token& currToken,
-            const dictionary&,
-            Istream&
-        );
+        void append(const token& currToken, const dictionary&, Istream&);
 
-        //- Expand the given variable (keyword starts with $)
-        bool expandVariable(const string&, const dictionary&);
+        //- Expand the given variable
+        bool expandVariable(const variable&, const dictionary&);
 
         //- Expand the given function (keyword starts with #)
-        bool expandFunction
-        (
-            const word&,
-            const dictionary&,
-            Istream&
-        );
+        bool expandFunction(const word&, const dictionary&, Istream&);
 
         //- Read the complete entry from the given stream
         void readEntry(const dictionary&, Istream&);
diff --git a/src/OpenFOAM/db/dictionary/primitiveEntry/primitiveEntryIO.C b/src/OpenFOAM/db/dictionary/primitiveEntry/primitiveEntryIO.C
index 99b73704b1..68a824e78f 100644
--- a/src/OpenFOAM/db/dictionary/primitiveEntry/primitiveEntryIO.C
+++ b/src/OpenFOAM/db/dictionary/primitiveEntry/primitiveEntryIO.C
@@ -60,7 +60,7 @@ void Foam::primitiveEntry::append
         (
             disableFunctionEntries
          || v.size() == 1
-         || !(v[0] == '$' && expandVariable(v, dict))
+         || !expandVariable(v, dict)
         )
         {
             newElmt(tokenIndex()++) = currToken;
diff --git a/src/OpenFOAM/meshes/polyMesh/polyPatches/constraint/processorCyclic/processorCyclicPolyPatch.C b/src/OpenFOAM/meshes/polyMesh/polyPatches/constraint/processorCyclic/processorCyclicPolyPatch.C
index bb7ba6185c..c9a09f35b1 100644
--- a/src/OpenFOAM/meshes/polyMesh/polyPatches/constraint/processorCyclic/processorCyclicPolyPatch.C
+++ b/src/OpenFOAM/meshes/polyMesh/polyPatches/constraint/processorCyclic/processorCyclicPolyPatch.C
@@ -178,7 +178,7 @@ Foam::labelList Foam::processorCyclicPolyPatch::patchIDs
 {
     return bm.findIndices
     (
-        string("procBoundary.*to.*through" + cyclicPolyPatchName)
+        keyType(string("procBoundary.*to.*through" + cyclicPolyPatchName))
     );
 }
 
diff --git a/src/OpenFOAM/primitives/strings/keyType/keyType.C b/src/OpenFOAM/primitives/strings/keyType/keyType.C
index fc2bd75a6f..1604dc49dd 100644
--- a/src/OpenFOAM/primitives/strings/keyType/keyType.C
+++ b/src/OpenFOAM/primitives/strings/keyType/keyType.C
@@ -21,9 +21,6 @@ License
     You should have received a copy of the GNU General Public License
     along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
 
-Description
-    Istream constructor and IOstream operators for keyType.
-
 \*---------------------------------------------------------------------------*/
 
 #include "keyType.H"
@@ -37,10 +34,19 @@ const Foam::keyType Foam::keyType::null;
 
 // * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //
 
+Foam::keyType::keyType(const token& t)
+:
+    variable(),
+    type_(UNDEFINED)
+{
+    operator=(t);
+}
+
+
 Foam::keyType::keyType(Istream& is)
 :
     variable(),
-    isPattern_(false)
+    type_(UNDEFINED)
 {
     is  >> *this;
 }
@@ -54,19 +60,52 @@ bool Foam::keyType::match
     bool literalMatch
 ) const
 {
-    if (literalMatch || !isPattern_)
+    if (literalMatch || !isPattern())
     {
-        // check as string
+        // Check as string
         return (str == *this);
     }
     else
     {
-        // check as regex
+        // Check as regex
         return regExp(*this).match(str);
     }
 }
 
 
+// * * * * * * * * * * * * * * * Member Operators  * * * * * * * * * * * * * //
+
+void Foam::keyType::operator=(const token& t)
+{
+    if (t.isWord())
+    {
+        operator=(t.wordToken());
+    }
+    else if (t.isVariable())
+    {
+        operator=(t.variableToken());
+    }
+    else if (t.isString())
+    {
+        // Assign from string. Set as pattern.
+        operator=(t.stringToken());
+
+        // An empty pattern string is a fatal error
+        if (empty())
+        {
+            FatalErrorInFunction
+                << "Empty pattern string"
+                << exit(FatalIOError);
+        }
+    }
+    else
+    {
+        variable::clear();
+        type_ = UNDEFINED;
+    }
+}
+
+
 // * * * * * * * * * * * * * * * IOstream Operators  * * * * * * * * * * * * //
 
 Foam::Istream& Foam::operator>>(Istream& is, keyType& kw)
@@ -79,27 +118,9 @@ Foam::Istream& Foam::operator>>(Istream& is, keyType& kw)
         return is;
     }
 
-    if (t.isWord())
-    {
-        kw = t.wordToken();
-    }
-    else if (t.isString())
-    {
-        // Assign from string. Set as regular expression.
-        kw = t.stringToken();
-        kw.isPattern_ = true;
+    kw = t;
 
-        // flag empty strings as an error
-        if (kw.empty())
-        {
-            is.setBad();
-            FatalIOErrorInFunction(is)
-                << "empty word/expression "
-                << exit(FatalIOError);
-            return is;
-        }
-    }
-    else
+    if (kw.isUndefined())
     {
         is.setBad();
         FatalIOErrorInFunction(is)
diff --git a/src/OpenFOAM/primitives/strings/keyType/keyType.H b/src/OpenFOAM/primitives/strings/keyType/keyType.H
index e058d21268..0d7090b77b 100644
--- a/src/OpenFOAM/primitives/strings/keyType/keyType.H
+++ b/src/OpenFOAM/primitives/strings/keyType/keyType.H
@@ -48,6 +48,7 @@ namespace Foam
 // Forward declaration of classes
 class Istream;
 class Ostream;
+class token;
 
 
 // Forward declaration of friend functions and operators
@@ -66,16 +67,20 @@ class keyType
 :
     public variable
 {
+    //- Enumeration of the keyword types
+    enum type
+    {
+        UNDEFINED,
+        WORD,
+        VARIABLE,
+        PATTERN
+    };
+
+
     // Private Data
 
-        //- Is the keyType a pattern (regular expression)
-        bool isPattern_;
-
-
-    // Private Member Functions
-
-        //- Disallow assignments where we cannot determine string/word type
-        void operator=(const std::string&);
+        //- The type of this keyword
+        type type_;
 
 
 public:
@@ -94,29 +99,33 @@ public:
         //- Copy constructor
         inline keyType(const keyType&);
 
-        //- Copy constructor of variable. Not treated as a regular expression
-        inline keyType(const variable&);
-
-        //- Copy constructor of word. Not treated as a regular expression
+        //- Construct as word
         inline keyType(const word&);
 
-        //- Copy constructor of string. Treat as regular expression.
-        inline keyType(const string&);
+        //- Construct as variable
+        inline explicit keyType(const variable&);
 
-        //- Copy constructor of character array.
-        //  Not treated as a regular expression
+        //- Construct as pattern
+        inline explicit keyType(const string&);
+
+        //- Construct as word from character array.
         inline keyType(const char*);
 
-        //- Copy constructor of std::string with specified treatment
-        inline keyType(const std::string&, const bool isPattern);
+        //- Construct from token
+        explicit keyType(const token&);
 
         //- Construct from Istream
-        //  Treat as regular expression if surrounded by quotation marks.
-        keyType(Istream&);
+        explicit keyType(Istream&);
 
 
     // Member Functions
 
+        //- Return true if the type has not been defined
+        inline bool isUndefined() const;
+
+        //- Return true if the keyword is a variable
+        inline bool isVariable() const;
+
         //- Should be treated as a match rather than a literal string
         inline bool isPattern() const;
 
@@ -132,18 +141,24 @@ public:
             //- Assignment operator
             inline void operator=(const keyType&);
 
-            //- Assign as variable, not as non regular expression
+            //- Assign as variable
             inline void operator=(const variable&);
 
-            //- Assign as word, not as non regular expression
+            //- Assign as word
             inline void operator=(const word&);
 
-            //- Assign as regular expression
+            //- Assign as pattern
             inline void operator=(const string&);
 
-            //- Assign as word, not as non regular expression
+            //- Assign as word
             inline void operator=(const char*);
 
+            //- Disallow assignments where we cannot determine string/word type
+            void operator=(const std::string&) = delete;
+
+            //- Assign from token setting the appropriate type
+            void operator=(const token&);
+
 
     // IOstream Operators
 
diff --git a/src/OpenFOAM/primitives/strings/keyType/keyTypeI.H b/src/OpenFOAM/primitives/strings/keyType/keyTypeI.H
index e5ba881a94..b720dddf91 100644
--- a/src/OpenFOAM/primitives/strings/keyType/keyTypeI.H
+++ b/src/OpenFOAM/primitives/strings/keyType/keyTypeI.H
@@ -28,57 +28,62 @@ License
 inline Foam::keyType::keyType()
 :
     variable(),
-    isPattern_(false)
+    type_(UNDEFINED)
 {}
 
 
 inline Foam::keyType::keyType(const keyType& k)
 :
     variable(k),
-    isPattern_(k.isPattern())
+    type_(k.type_)
 {}
 
 
 inline Foam::keyType::keyType(const word& w)
 :
     variable(w),
-    isPattern_(false)
+    type_(WORD)
 {}
 
 
 inline Foam::keyType::keyType(const variable& v)
 :
     variable(v),
-    isPattern_(false)
+    type_(VARIABLE)
 {}
 
 
 inline Foam::keyType::keyType(const string& s)
 :
     variable(s, false),
-    isPattern_(true)
+    type_(PATTERN)
 {}
 
 
 inline Foam::keyType::keyType(const char* s)
 :
-    variable(s, false),
-    isPattern_(false)
-{}
-
-
-inline Foam::keyType::keyType(const std::string& s, const bool isPattern)
-:
-    variable(s, false),
-    isPattern_(isPattern)
+    variable(s, true),
+    type_(WORD)
 {}
 
 
 // * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
 
+inline bool Foam::keyType::isUndefined() const
+{
+    return type_ == UNDEFINED;
+}
+
+
+inline bool Foam::keyType::isVariable() const
+{
+    return type_ == VARIABLE;
+}
+
+
 inline bool Foam::keyType::isPattern() const
 {
-    return isPattern_;
+    return type_ == PATTERN;
 }
 
 
@@ -87,37 +92,35 @@ inline bool Foam::keyType::isPattern() const
 inline void Foam::keyType::operator=(const keyType& k)
 {
     variable::operator=(k);
-    isPattern_ = k.isPattern_;
-}
-
-
-inline void Foam::keyType::operator=(const variable& v)
-{
-    variable::operator=(v);
-    isPattern_ = false;
+    type_ = k.type_;
 }
 
 
 inline void Foam::keyType::operator=(const word& w)
 {
     variable::operator=(w);
-    isPattern_ = false;
+    type_ = WORD;
+}
+
+
+inline void Foam::keyType::operator=(const variable& v)
+{
+    variable::operator=(v);
+    type_ = VARIABLE;
 }
 
 
 inline void Foam::keyType::operator=(const string& s)
 {
-    // Bypass checking
     string::operator=(s);
-    isPattern_ = true;
+    type_ = PATTERN;
 }
 
 
 inline void Foam::keyType::operator=(const char* s)
 {
-    // Bypass checking
-    string::operator=(s);
-    isPattern_ = false;
+    word::operator=(s);
+    type_ = WORD;
 }
 
 
diff --git a/src/OpenFOAM/primitives/strings/variable/variable.H b/src/OpenFOAM/primitives/strings/variable/variable.H
index fa908500e6..430d9a7d8b 100644
--- a/src/OpenFOAM/primitives/strings/variable/variable.H
+++ b/src/OpenFOAM/primitives/strings/variable/variable.H
@@ -86,20 +86,24 @@ public:
         inline variable(const variable&);
 
         //- Copy constructor of word
-        inline variable(const word&);
+        inline explicit variable(const word&);
 
         //- Copy constructor of string
-        inline variable(const string&, const bool doStripInvalid=true);
+        inline explicit variable(const string&, const bool doStripInvalid=true);
 
         //- Copy constructor of std::string
-        inline variable(const std::string&, const bool doStripInvalid=true);
+        inline explicit variable
+        (
+            const std::string&,
+            const bool doStripInvalid=true
+        );
 
         //- Copy constructor of character array
-        inline variable(const char*, const bool doStripInvalid=true);
+        inline explicit variable(const char*, const bool doStripInvalid=true);
 
         //- Construct from Istream
         //  Words are treated as literals, strings with an auto-test
-        variable(Istream&);
+        explicit variable(Istream&);
 
 
     // Member Functions