10ten Japanese Reader (Rikaichamp)

Quickly look up Japanese words on any text page by activating the add-on from the toolbar (you may need to use the Extensions menu to pin the icon to the toolbar) or pressing Alt+R.

Features:

• Pitch accent information

• Dictionaries that update automatically twice a week

• Recognition of a wide range of grammatical forms and characters (e.g. 食べてた, 分からん, 知らん, じーちゃん, 頑張ろー, そーゆー, ぬ verbs, とく・どく forms, causative passive, vs-c verbs like 兼した, and characters like ㋕, ㌀, ㋿, 𠏹沢, and many more)

• Translation of Japanese numbers into Arabic numerals (e.g. 13億5千万 into 1,350,000,000)