The Meaning of the Term "Gospel"

The greek word for "gospel" is euangelion and it means good tidings, or good news. Euangelizomai is the verb form , which means "proclaim or preach the gospel" , The term "gospel" originally referred to the "reward" given to a messenger who brought the news , and it soon became identified with the news itself.

Paul's letters are the earliest  NT writings in which euangelion  directly refers to God's saving act in Christ .Paul uses the term in an absolute sense : that is, the gospel is complete , requiring neither embellishment nor qualitative description . It is one and there can be no other (Gal 1:7). It originated with God and was revealed to Paul by God (not by human agent). Paul's authority as an apostle  is grounded in the gospel he understands to be the gospel of God and of "his son" , Jesus Christ (Rom 1:1-5).This is gospel to which Paul has responded and by which he now functions is the story of Jesus Christ (Phil 2: 6-11) including his sufferings, death , and resurrection ( glorification)
The content of the gospel find striking affinity with the prophetic oracle of the suffering servant in Isaiah 53. This Gospel is totally sufficient for for salvation and it is freely given by God's grace to be received by faith that finds full expression in the actions of all who believe .

According to the Church the term gospel takes on a literary character with the first four books of the NT canon: the "gospels" according to Matthew, Mark Luke, and John. In these books of the good news is presented in the form of the story of Jesus Christ including an account of of his birth, ministry, death and resurrection . Although Mark is the only author who specifically refers to his narrative of Jesus as a gospel (Mark 1:1) the term become accepted canonical title for all four of the NT accounts of Jesus along with the  several other noncanonical works that present  traditions related to Jesus. Gospel therefore refers to the refers to the good news of Salvation through Jesus Christ as in  the Pauline letters ; it also refers to a type of type of literature revered in various christian communities.

This literature may contain a presentation of the story of Jesus Christ as set forth in a narrative "biography" form , it may take the forms of tradition presented as Jesus' sayings or it may present material topically organized around specific events in Jesus' life . Clearly the dynamic concept of the gospel of Jesus Christ  as proclaimed by Paul and other early Christian  evangelists provided the conditions in which the term gospel become the literary designator for those books containing the story or traditions related to the story of Jesus Christ.