Andrew Ozz

This plugin adds 30 languages to <a href="https://wordpress.org/plugins/tinymce-advanced/" rel="ugc">TinyMCE Advanced</a>: 
Arabic (ar), Belarusian (be), Bokmål Norwegian (nb), Bulgarian (bg), Catalan (ca), Simplified Chinese (cn), Czech (cs), Danish (da), Dutch, Flemish (nl), Farsi (fa), Finnish (fi), Galician (gl), Greek (el), Hebrew (he), Hungarian (hu), Indonesian (id), Central Khmer (km), Korean (ko), Latvian (lv), Lithuanian (lt), Macedonian (mk), Norwegian (no), Polish (pl), Romanian (ro), Slovak (sk), Slovenian (sl), Swedish (sv), Turkish (tr), Ukrainian (uk), Welsh (cy).
If you have set WordPress to one of these languages and this plugin is enabled, the TinyMCE Advanced plugin will use that language for all buttons and popups added to the Visual editor.

TinyMCE Advanced Language Pack

Adds more translations for the TinyMCE components used in the TinyMCE Advanced plugin.

russtek

This extension makes it easier to proof your writing with the Slick Write web service. Analyze your work’s flow, check for the passive voice, eliminate unnecessary adverbs, and much more.

TinyMCE Advanced Language Pack vs Slick Write