Okurigana are the hiragana that come after a kanji to complete a word.
For example, if you want to write あたらしい (”new”) using kanji, it would look like this:
新しい
The two hiragana characters し and い are the “okurigana” that complete the word.
In each kanji entry on KanjiHacks.com, the okurigana are indicated by an underline.
