Patch-Magento-Framework-Translate_M2.2.5-theme-inherit-translations.patch

--- Translate.php
+++ Translate.php
@@ -328,17 +328,78 @@ class Translate implements \Magento\Framework\TranslateInterface
 
     /**
      * Load current theme translation
+     * Fix: Child theme does not inherit translations from parent theme 
      *
      * @return $this
      */
     protected function _loadThemeTranslation()
     {
-        $file = $this->_getThemeTranslationFile($this->getLocale());
-        if ($file) {
-            $this->_addData($this->_getFileData($file));
+        $themeFiles = $this->getThemeTranslationFilesList($this->getLocale());
+
+        /** @var string $file */
+        foreach ($themeFiles as $file) {
+            if ($file) {
+                $this->_addData($this->_getFileData($file));
+            }
         }
+
         return $this;
     }
+    
+    /**
+     * 
+     * Fix: Child theme does not inherit translations from parent theme
+     * 
+     */
+    private function getThemeTranslationFilesList($locale)
+    {
+        $translationFiles = [];
+
+        /** @var \Magento\Framework\View\Design\ThemeInterface $theme */
+        foreach ($this->getParentThemesList() as $theme) {
+            $config = $this->_config;
+            $config['theme'] = $theme->getCode();
+            $translationFiles[] = $this->getThemeTranslationFileName($locale, $config);
+        }
+
+        $translationFiles[] = $this->getThemeTranslationFileName($locale, $this->_config);
+
+        return $translationFiles;
+    }
+
+
+    /**
+     * 
+     * Fix: Child theme does not inherit translations from parent theme
+     * 
+     */
+    private function getParentThemesList()
+    {
+        $themes = [];
+
+        $parentTheme = $this->_viewDesign->getDesignTheme()->getParentTheme();
+        while($parentTheme) {
+            $themes[] = $parentTheme;
+            $parentTheme = $parentTheme->getParentTheme();
+        }
+        $themes = array_reverse($themes);
+
+        return $themes;
+    }
+
+    /**
+     * 
+     * Fix: Child theme does not inherit translations from parent theme
+     * 
+     */
+    private function getThemeTranslationFileName($locale, $config)
+    {
+        return $this->_viewFileSystem->getLocaleFileName(
+            'i18n' . '/' . $locale . '.csv',
+            $config
+        );
+    }
+
 
     /**
      * Load translation dictionary from language packages