diff --git a/CHANGES.md b/CHANGES.md
index 9061a346cb..b9ef99e36d 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -19,6 +19,9 @@ Language Improvements:
 
 - fix(javascript) prevent get/set variables conflicting with keywords (#2440) [Josh Goebel][]
 - bug(clojure) Now highlights `defn-` properly (#2438) [Josh Goebel][]
+- enh(bash) default value is another variable (#2439) [Josh Goebel][]
+- enh(bash) string nested within string (#2439) [Josh Goebel][]
+- enh(bash) Add arithmetic expression support (#2439) [Josh Goebel][]
 - enh(clojure) Add support for global definitions name (#2347) [Alexandre Grison][]
 - enh(fortran) Support Fortran 77 style comments (#2416) [Josh Goebel][]
 - (csharp) add support for `@identifier` style identifiers (#2414) [Josh Goebel][]
diff --git a/src/languages/bash.js b/src/languages/bash.js
index 3d37ded159..be9c8c92fc 100644
--- a/src/languages/bash.js
+++ b/src/languages/bash.js
@@ -7,35 +7,66 @@ Category: common
 */
 
 export default function(hljs) {
-  var VAR = {
+  const VAR = {};
+  const BRACED_VAR = {
+    begin: /\$\{/, end:/\}/,
+    contains: [
+      { begin: /:-/, contains: [VAR] } // default values
+    ]
+  };
+  Object.assign(VAR,{
     className: 'variable',
     variants: [
       {begin: /\$[\w\d#@][\w\d_]*/},
-      {begin: /\$\{(.*?)}/}
+      BRACED_VAR
     ]
+  });
+
+  const SUBST = {
+    className: 'subst',
+    begin: /\$\(/, end: /\)/,
+    contains: [hljs.BACKSLASH_ESCAPE]
   };
-  var QUOTE_STRING = {
+  const QUOTE_STRING = {
     className: 'string',
     begin: /"/, end: /"/,
     contains: [
       hljs.BACKSLASH_ESCAPE,
       VAR,
-      {
-        className: 'variable',
-        begin: /\$\(/, end: /\)/,
-        contains: [hljs.BACKSLASH_ESCAPE]
-      }
+      SUBST
     ]
   };
-  var ESCAPED_QUOTE = {
+  SUBST.contains.push(QUOTE_STRING);
+  const ESCAPED_QUOTE = {
     className: '',
     begin: /\\"/
 
   };
-  var APOS_STRING = {
+  const APOS_STRING = {
     className: 'string',
     begin: /'/, end: /'/
   };
+  const ARITHMETIC = {
+    begin: /\$\(\(/,
+    end: /\)\)/,
+    contains: [
+      { begin: /\d+#[0-9a-f]+/, className: "number" },
+      hljs.NUMBER_MODE,
+      VAR
+    ]
+  };
+  const SHEBANG = {
+    className: 'meta',
+    begin: /^#![^\n]+sh\s*$/,
+    relevance: 10
+  };
+  const FUNCTION = {
+    className: 'function',
+    begin: /\w[\w\d_]*\s*\(\s*\)\s*\{/,
+    returnBegin: true,
+    contains: [hljs.inherit(hljs.TITLE_MODE, {begin: /\w[\w\d_]*/})],
+    relevance: 0
+  };
 
   return {
     name: 'Bash',
@@ -67,18 +98,9 @@ export default function(hljs) {
         '-ne -eq -lt -gt -f -d -e -s -l -a' // relevance booster
     },
     contains: [
-      {
-        className: 'meta',
-        begin: /^#![^\n]+sh\s*$/,
-        relevance: 10
-      },
-      {
-        className: 'function',
-        begin: /\w[\w\d_]*\s*\(\s*\)\s*\{/,
-        returnBegin: true,
-        contains: [hljs.inherit(hljs.TITLE_MODE, {begin: /\w[\w\d_]*/})],
-        relevance: 0
-      },
+      SHEBANG,
+      FUNCTION,
+      ARITHMETIC,
       hljs.HASH_COMMENT_MODE,
       QUOTE_STRING,
       ESCAPED_QUOTE,
diff --git a/test/markup/bash/arithmetic.expect.txt b/test/markup/bash/arithmetic.expect.txt
new file mode 100644
index 0000000000..28ebd37413
--- /dev/null
+++ b/test/markup/bash/arithmetic.expect.txt
@@ -0,0 +1,8 @@
+<span class="hljs-built_in">echo</span> $(( <span class="hljs-number">16#deadbeef</span> / <span class="hljs-number">1003</span> ))
+
+yumi=deadbeef
+<span class="hljs-built_in">echo</span> $(( <span class="hljs-number">16</span>#<span class="hljs-variable">$yumi</span> / <span class="hljs-number">1003</span> ))
+
+B=20
+yumi=deadbeef
+<span class="hljs-built_in">echo</span> $(( <span class="hljs-variable">$B</span>#<span class="hljs-variable">$yumi</span> / <span class="hljs-number">1003</span> ))
diff --git a/test/markup/bash/arithmetic.txt b/test/markup/bash/arithmetic.txt
new file mode 100644
index 0000000000..d44dea465e
--- /dev/null
+++ b/test/markup/bash/arithmetic.txt
@@ -0,0 +1,8 @@
+echo $(( 16#deadbeef / 1003 ))
+
+yumi=deadbeef
+echo $(( 16#$yumi / 1003 ))
+
+B=20
+yumi=deadbeef
+echo $(( $B#$yumi / 1003 ))
diff --git a/test/markup/bash/strings.expect.txt b/test/markup/bash/strings.expect.txt
new file mode 100644
index 0000000000..39abcc1b1d
--- /dev/null
+++ b/test/markup/bash/strings.expect.txt
@@ -0,0 +1,3 @@
+SCRIPT_DIR=<span class="hljs-string">"<span class="hljs-subst">$( cd <span class="hljs-string">"<span class="hljs-subst">$( dirname <span class="hljs-string">"<span class="hljs-variable">${BASH_SOURCE[0]}</span>"</span> )</span>"</span> &gt;/dev/null 2&gt;&amp;1 &amp;&amp; pwd )</span>"</span>
+TLS_DIR=<span class="hljs-string">"<span class="hljs-variable">$SCRIPT_DIR</span>/../src/main/resources/tls"</span>
+ROOT_DIR=<span class="hljs-string">"<span class="hljs-variable">$SCRIPT_DIR</span>/.."</span>
diff --git a/test/markup/bash/strings.txt b/test/markup/bash/strings.txt
new file mode 100644
index 0000000000..c2d7f55732
--- /dev/null
+++ b/test/markup/bash/strings.txt
@@ -0,0 +1,3 @@
+SCRIPT_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" >/dev/null 2>&1 && pwd )"
+TLS_DIR="$SCRIPT_DIR/../src/main/resources/tls"
+ROOT_DIR="$SCRIPT_DIR/.."
diff --git a/test/markup/bash/variables.expect.txt b/test/markup/bash/variables.expect.txt
new file mode 100644
index 0000000000..708b15f2f2
--- /dev/null
+++ b/test/markup/bash/variables.expect.txt
@@ -0,0 +1,3 @@
+<span class="hljs-variable">$A</span>
+<span class="hljs-variable">${B}</span>
+<span class="hljs-variable">${WURST:-<span class="hljs-variable">${CARNE}</span>}</span>
diff --git a/test/markup/bash/variables.txt b/test/markup/bash/variables.txt
new file mode 100644
index 0000000000..eb89ed0cda
--- /dev/null
+++ b/test/markup/bash/variables.txt
@@ -0,0 +1,3 @@
+$A
+${B}
+${WURST:-${CARNE}}