diff --git a/frontend/apps/reader/modules/readerdictionary.lua b/frontend/apps/reader/modules/readerdictionary.lua
index b1a57dfc6..258938fad 100644
--- a/frontend/apps/reader/modules/readerdictionary.lua
+++ b/frontend/apps/reader/modules/readerdictionary.lua
@@ -811,7 +811,7 @@ function ReaderDictionary:startSdcv(word, dict_names, fuzzy_search)
         end
     end
 
-    lookup_cancelled, results = self:rawSdcv(words, dict_names, fuzzy_search, self.lookup_progress_msg or false)
+    local lookup_cancelled, results = self:rawSdcv(words, dict_names, fuzzy_search, self.lookup_progress_msg or false)
     if results == nil then -- no dictionaries found
         return {
             {
diff --git a/frontend/languagesupport.lua b/frontend/languagesupport.lua
index ee9906b1d..38d732a1c 100644
--- a/frontend/languagesupport.lua
+++ b/frontend/languagesupport.lua
@@ -20,7 +20,6 @@ knowledge may be necessary (such as during text selection and dictionary lookup
 of a text fragment).
 ]]
 
-local UIManager = require("ui/uimanager")
 local WidgetContainer = require("ui/widget/container/widgetcontainer")
 local dbg = require("dbg")
 local logger = require("logger")
@@ -115,8 +114,8 @@ local function callPlugin(plugin, handler_name, ...)
         return
     end
     -- Handler could return any number of values, collect them all.
-    ret = {pcall(handler, plugin, ...)}
-    ok = table.remove(ret, 1)
+    local ret = {pcall(handler, plugin, ...)}
+    local ok = table.remove(ret, 1)
     if not ok then
         logger.err("language plugin", plugin, "crashed during", handler_name, "handler:", unpack(ret))
         return
@@ -130,7 +129,7 @@ function LanguageSupport:_findAndCallPlugin(language_code, handler_name, ...)
     for name, plugin in pairs(self.plugins) do
         if plugin:supportsLanguage(language_code) then
             logger.dbg("language support: trying", name, "plugin's", handler_name)
-            ret = callPlugin(plugin, handler_name, ...)
+            local ret = callPlugin(plugin, handler_name, ...)
             if ret ~= nil then
                 return unpack(ret)
             end
@@ -143,7 +142,7 @@ function LanguageSupport:_findAndCallPlugin(language_code, handler_name, ...)
     for name, plugin in pairs(self.plugins) do
         if not plugin:supportsLanguage(language_code) then
             logger.dbg("language support (fallback): trying", name, "plugin's", handler_name)
-            ret = callPlugin(plugin, handler_name, ...)
+            local ret = callPlugin(plugin, handler_name, ...)
             if ret ~= nil then
                 return unpack(ret)
             end
@@ -195,14 +194,14 @@ function LanguageSupport:improveWordSelection(selection)
         return
     end
 
-    language_code = self.document:getProps().language or "unknown"
+    local language_code = self.document:getProps().language or "unknown"
     logger.dbg("language support: improving", language_code, "selection", selection)
 
     -- Rather than requiring each language plugin to use document: methods
     -- correctly, return a set of callbacks that are document-agnostic (and
     -- have the document handle as an upvalue of the closure) and could be used
     -- for non-EPUB formats in the future.
-    callbacks = createDocumentCallbacks(self.document)
+    local callbacks = createDocumentCallbacks(self.document)
     if not callbacks then
         return
     end
@@ -251,7 +250,7 @@ end
 function LanguageSupport:extraDictionaryFormCandidates(text)
     if not self:hasActiveLanguagePlugins() then return end -- nothing to do
 
-    language_code = self.document and self.document:getProps().language or "unknown"
+    local language_code = self.document and self.document:getProps().language or "unknown"
     logger.dbg("language support: convert", text, "to dictionary form (marked as", language_code..")")
 
     return self:_findAndCallPlugin(
@@ -263,16 +262,17 @@ end
 function LanguageSupport:addToMainMenu(menu_items)
     if not self:hasActiveLanguagePlugins() then return end -- nothing to do
 
-    local sub_table = {}
-
     -- Sort the plugin keys so we have consistent ordering in the menu.
     local plugin_names = {}
     for name in pairs(self.plugins) do
         table.insert(plugin_names, name)
     end
     table.sort(plugin_names)
+
+    -- Link up each plugin's submenu.
+    local sub_table = {}
     for _, name in ipairs(plugin_names) do
-        plugin = self.plugins[name]
+        local plugin = self.plugins[name]
         if plugin.genMenuItem ~= nil then
             local menuItem = plugin:genMenuItem()
             -- Set help_text in case the plugin hasn't.
@@ -281,8 +281,8 @@ function LanguageSupport:addToMainMenu(menu_items)
             end
             table.insert(sub_table, menuItem)
         else
-            -- A basic fallback menu, showing a description of the plugin when
-            -- tapped (if supplied).
+            -- Plugin didn't have a menu defined so use a basic fallback menu,
+            -- showing a description of the plugin when held for help.
             table.insert(sub_table, {
                 text = plugin.pretty_name or plugin.fullname or name,
                 help_text = plugin.description,
diff --git a/frontend/util.lua b/frontend/util.lua
index c298a4f70..99779e953 100644
--- a/frontend/util.lua
+++ b/frontend/util.lua
@@ -601,7 +601,7 @@ function util.isCJKChar(c)
     if #c < 3 then
         return false
     end
-    code = BaseUtil.utf8charcode(c)
+    local code = BaseUtil.utf8charcode(c)
     -- The weird bracketing is intentional -- we use the lowest possible
     -- codepoint as a shortcut so if the codepoint is below U+1100 we
     -- immediately return false.
diff --git a/plugins/japanese.koplugin/deinflector.lua b/plugins/japanese.koplugin/deinflector.lua
index 72b3a9dd0..68db9b323 100644
--- a/plugins/japanese.koplugin/deinflector.lua
+++ b/plugins/japanese.koplugin/deinflector.lua
@@ -37,7 +37,7 @@ local RULE_TYPES = {
 }
 
 local function toRuleTypes(...)
-    final = 0
+    local final = 0
     for _, ruleType in ipairs({...}) do
         if RULE_TYPES[ruleType] then
             final = bit.bor(final, RULE_TYPES[ruleType])
@@ -102,7 +102,7 @@ function Deinflector:deinflectVerbatim(text)
                     -- Check if we've already found this deinflection. If so,
                     -- that means there was a shorter reason path to it and
                     -- this deinflection is almost certainly theoretical.
-                    new_term = current.term:sub(1, -#rule.kanaIn-1) .. rule.kanaOut
+                    local new_term = current.term:sub(1, -#rule.kanaIn-1) .. rule.kanaOut
                     if not seen[new_term] then
                         table.insert(results, makeDeinflectionResult(
                             new_term,
@@ -435,14 +435,14 @@ function Deinflector:init()
                                     DEFAULT_TEXT_CONVERSIONS
     if self.rules ~= nil then return end -- already loaded
 
-    --- @todo Maybe make this location configurable?
-    inflections = parsePluginJson("yomichan-deinflect.json")
+    --- @todo Maybe make this location configurable or look in the user-controlled data directory too?
+    local inflections = parsePluginJson("yomichan-deinflect.json")
 
     -- Normalise the reasons and convert the rules to the rule_types bitflags.
     self.rules = {}
     local nrules, nvariants = 0, 0
     for reason, rules in pairs(inflections) do
-        variants = {}
+        local variants = {}
         for i, variant in ipairs(rules) do
             variants[i] = {
                 kanaIn = variant.kanaIn,
diff --git a/plugins/japanese.koplugin/main.lua b/plugins/japanese.koplugin/main.lua
index 37d873b5a..8d544c5e6 100644
--- a/plugins/japanese.koplugin/main.lua
+++ b/plugins/japanese.koplugin/main.lua
@@ -19,11 +19,9 @@
 -- together in order to reduce the impact we have on text selection.
 
 local Deinflector = require("deinflector")
-local InfoMessage = require("ui/widget/infomessage")
 local LanguageSupport = require("languagesupport")
 local ReaderDictionary = require("apps/reader/modules/readerdictionary")
 local UIManager = require("ui/uimanager")
-local JSON = require("json")
 local WidgetContainer = require("ui/widget/container/widgetcontainer")
 local logger = require("logger")
 local util = require("util")
@@ -77,7 +75,7 @@ function Japanese:onWordLookup(args)
     --       extra work to be efficient (since we need to remove the last
     --       character in the string).
 
-    results = self.deinflector:deinflect(text)
+    local results = self.deinflector:deinflect(text)
     logger.dbg("japanese.koplugin: deinflection of", text, "results:", results)
 
     --- @todo Pass up the reasons list (formatted Yomichan style) to the
@@ -86,7 +84,7 @@ function Japanese:onWordLookup(args)
     --       metadata that we have to pass through from the lookup to the
     --       dictionary pop-up.
 
-    candidates = {}
+    local candidates = {}
     for i, result in ipairs(results) do
         candidates[i] = result.term
     end
@@ -112,7 +110,6 @@ end
 -- @see languagesupport.improveWordSelection
 -- @see languagesupport.registerPlugin
 function Japanese:onWordSelection(args)
-    local pos0, pos1 = args.pos0, args.pos1
     local callbacks = args.callbacks
     local current_text = args.text
 
@@ -128,7 +125,7 @@ function Japanese:onWordSelection(args)
     -- We reset the end of the range to pos0+1 because crengine will select
     -- half-width katakana (ｶﾀｶﾅ) in strange ways that often overshoots the
     -- end of words.
-    pos1 = callbacks.get_next_char_pos(pos0)
+    local pos0, pos1 = args.pos0, callbacks.get_next_char_pos(args.pos0)
 
     -- We try to advance the end position until we hit a word.
     --