diff --git a/lib/parse.js b/lib/parse.js
index f274885..5368618 100644
--- a/lib/parse.js
+++ b/lib/parse.js
@@ -10,36 +10,36 @@ module.exports = parse
 
 var own = {}.hasOwnProperty
 
-var MAX_SUBTAG = 8
-var MAX_RESERVED = 4
-var MAX_ISO_639 = 3
-var MIN_ISO_639 = 2
-var MAX_EXTENDED_LANGUAGE_SUBTAG_COUNT = 3
-var MAX_VARIANT = 8
-var MIN_ALPHANUMERIC_VARIANT = 5
-var MIN_VARIANT = 4
-var MAX_EXTENSION = 8
-var MAX_PRIVATE_USE = 8
-
-var ERR_VARIANT_TOO_LONG = 1
-var ERR_EXTENSION_TOO_LONG = 2
-var ERR_TOO_MANY_SUBTAGS = 3
-var ERR_EMPTY_EXTENSION = 4
-var ERR_PRIVATE_USE_TOO_LONG = 5
-var ERR_EXTRA_CONTENT = 6
-
-var ERRORS = {}
-
-ERRORS[ERR_VARIANT_TOO_LONG] = 'Too long variant, expected at most 8 characters'
-ERRORS[ERR_EXTENSION_TOO_LONG] =
+var maxSubtag = 8
+var maxReserved = 4
+var maxIso639 = 3
+var minIso639 = 2
+var maxExtendedLanguageSubtagCount = 3
+var maxVariant = 8
+var minAlphanumericVariant = 5
+var minVariant = 4
+var maxExtension = 8
+var maxPrivateUse = 8
+
+var errVariantTooLong = 1
+var errExtensionTooLong = 2
+var errTooManySubtags = 3
+var errEmptyExtension = 4
+var errPrivateUseTooLong = 5
+var errExtraContent = 6
+
+var errors = {}
+
+errors[errVariantTooLong] = 'Too long variant, expected at most 8 characters'
+errors[errExtensionTooLong] =
   'Too long extension, expected at most 8 characters'
-ERRORS[ERR_TOO_MANY_SUBTAGS] =
+errors[errTooManySubtags] =
   'Too many extended language subtags, expected at most 3 subtags'
-ERRORS[ERR_EMPTY_EXTENSION] =
+errors[errEmptyExtension] =
   'Empty extension, extensions must have at least 2 characters of content'
-ERRORS[ERR_PRIVATE_USE_TOO_LONG] =
+errors[errPrivateUseTooLong] =
   'Too long private-use area, expected at most 8 characters'
-ERRORS[ERR_EXTRA_CONTENT] = 'Found superfluous content after tag'
+errors[errExtraContent] = 'Found superfluous content after tag'
 
 // Parse a BCP 47 language tag.
 /* eslint-disable complexity */
@@ -88,13 +88,13 @@ function parse(tag, options) {
   }
 
   // Parse a normal tag.
-  if (index < MIN_ISO_639 || index > MAX_SUBTAG) {
+  if (index < minIso639 || index > maxSubtag) {
     index = 0
   } else {
-    if (index > MAX_RESERVED) {
+    if (index > maxReserved) {
       // Subtag language.
       result.language = sensitive.slice(0, index)
-    } else if (index > MAX_ISO_639) {
+    } else if (index > maxIso639) {
       // Reserved language.
       result.language = sensitive.slice(0, index)
     } else {
@@ -110,8 +110,8 @@ function parse(tag, options) {
         alphabetical(char(index + 3)) &&
         !alphabetical(char(index + 4))
       ) {
-        if (groupCount >= MAX_EXTENDED_LANGUAGE_SUBTAG_COUNT) {
-          return fail(index, ERR_TOO_MANY_SUBTAGS)
+        if (groupCount >= maxExtendedLanguageSubtagCount) {
+          return fail(index, errTooManySubtags)
         }
 
         // Extended language subtag.
@@ -167,16 +167,16 @@ function parse(tag, options) {
         offset++
         count++
 
-        if (count > MAX_VARIANT) {
-          return fail(offset, ERR_VARIANT_TOO_LONG)
+        if (count > maxVariant) {
+          return fail(offset, errVariantTooLong)
         }
       }
 
-      if (count >= MIN_ALPHANUMERIC_VARIANT) {
+      if (count >= minAlphanumericVariant) {
         // Long variant.
         result.variants.push(sensitive.slice(index + 1, offset))
         index = offset
-      } else if (decimal(char(index + 1)) && count >= MIN_VARIANT) {
+      } else if (decimal(char(index + 1)) && count >= minVariant) {
         // Short variant.
         result.variants.push(sensitive.slice(index + 1, offset))
         index = offset
@@ -208,8 +208,8 @@ function parse(tag, options) {
         groupCount++
 
         while (alphanumeric(char(offset))) {
-          if (count > MAX_EXTENSION) {
-            return fail(offset, ERR_EXTENSION_TOO_LONG)
+          if (count > maxExtension) {
+            return fail(offset, errExtensionTooLong)
           }
 
           offset++
@@ -218,7 +218,7 @@ function parse(tag, options) {
       }
 
       if (!groupCount) {
-        return fail(offset, ERR_EMPTY_EXTENSION)
+        return fail(offset, errEmptyExtension)
       }
 
       // Extension.
@@ -243,8 +243,8 @@ function parse(tag, options) {
       count = 1
 
       while (alphanumeric(char(offset))) {
-        if (count >= MAX_PRIVATE_USE) {
-          return fail(offset, ERR_PRIVATE_USE_TOO_LONG)
+        if (count >= maxPrivateUse) {
+          return fail(offset, errPrivateUseTooLong)
         }
 
         offset++
@@ -257,7 +257,7 @@ function parse(tag, options) {
   }
 
   if (index !== tag.length) {
-    return fail(index, ERR_EXTRA_CONTENT)
+    return fail(index, errExtraContent)
   }
 
   return result
@@ -268,7 +268,7 @@ function parse(tag, options) {
 
   function fail(offset, code) {
     if (warning) {
-      warning(ERRORS[code], code, offset)
+      warning(errors[code], code, offset)
     }
 
     return forgiving ? result : empty()