Don Johnson

Here is the terminology I use and how I see it.

1. There are the 12, apostles, and Scripture authors.

2. The 12 are apostles, but an apostle is not necessarily one of the 12.  Indeed they can be apostles today, but not the 12, as they are all dead.

3. The 12 were given authority to make decisions, including what is in the NT, indeed some of the 12 were Scripture authors.  John was the last survivor of the 12.

4. The 12 lost 1 of their group when Judas betrayed Jesus, in order to have 12, they needed to add 1, as these 12 map to the 12 tribes of Israel.  However, none of these final 12 were replaced when they died, such as James did but was not replaced.

5. James the brother of Jesus is called an apostle but he was not one of the 12, similarly Shaul/Paul is called an apostle but he was not one of the 12.  James became the leader of the Jerusalem church in Acts 15, even tho Peter was still around, and Paul became apostle to the gentiles even tho the first gentile to become a believer was due to Peter.