祭祀 

Pinyin: jì sì 
Meaning：Sacrifice
Sentence: 他们以羔羊祭祀众神。They sacrificed a lamb to the gods.

More: 

祭： 

Pinyin: zhài,jì
Meaning: Offer sacrifice
Radical: 示
Stokes: 11
Traditional: 祭
Common words/Phrase:
祭奠 [jì diàn] 【hold a memorial ceremony for】
祭司 [jì sī] 【priest】
祭祖 [jì zǔ] 【ancestor worship】
祭坛 [jì tán] 【altar】
祭品 [jì pǐn] 【offering】

祀： 

Pinyin: sì
Meaning: Offer sacrifice to
Radical: 礻
Stokes: 7
Traditional: 祀
Common words/Phrase:
祀奉 [sì fèng] 【enshrine】 
祀殿 [sì diàn] 【memorial hall】
祠祀 [cí sì] 【to offer sacrifice to gods in memorial temples】