Semantics is a science that has gained an important place in modern Quranic studies and has a significant impact on understanding the divine verses. And by considering the word's substitutes and companions, and then understanding the wisdom of the words and their placement in the context of the Quranic sentences, the present study seeks to understand the semantic component of the root "Ajr" in the Quran using the semantic method and based on the relationships of companionship and substitution. The companions of Ajr are 14 words and phrases, the most important of which are "Azeem, Kabeer, Karim". The substitute words are also four cases of "Thawab, Khair, Fawz, Jaza" which have been used a total of 93 times in verses related to "Ajr". The study of the companions and substitutes of the root "Ajr" shows that there are numerous semantic components in the semantic domain of Ajr; Among them, "the inclusion of material and spiritual rewards, the inclusion of worldly and hereafter rewards, good deeds, which can be acquired by God's servant, can be measured based on the level of faith, the result of the action, and the fact that the reward is granted and certain from God" is noteworthy.