IPA: /ˌæpəˈstɒlɪsɪti/
KK: /ˌæpəˈstɑlɪsɪti/
The quality of being related to the apostles, especially in maintaining the original teachings and traditions of the Christian church as established by Jesus and his twelve apostles.
The apostolicity of the church is essential for preserving its teachings over the centuries.
Apostolicity → It is formed from "apostolic" (from Greek "apostolos", meaning one who is sent) and the suffix "-ity" (meaning the state or condition of). The word "apostolicity" refers to the state or condition of being apostolic or relating to the apostles.
Think of the word 'apostolic' which means 'one who is sent' and remember that 'apostolicity' refers to the state of being related to those sent, like the apostles.
No commonly confused words.