期 is one of the most commonly used Japanese kanji, and it also has a lot of special readings in addition to the standard onyomi and kunyomi readings.
ONYOMI 音読み
KUNYOMI 訓読み
キ ki ゴ go
Examples
経済は景気後退期に入った。The economy has entered a recession.これはターナーの円熟期の作品です。This is a work from Turner’s mature period.シェイクスピアの劇は四期に分かれる。The plays of Shakespeare fall into four periods.