IPA: /vɛkˈsɪləˌlɑdʒi/
KK: /vɛkˌsɪlˈɑlədʒi/
The study of flags and their symbolism, history, and usage.
He is passionate about vexillology and has a large collection of flags from around the world.
Vexillology is formed from "vexillum" (Latin for flag or banner) and "-logy" (from Greek "logia", meaning study or discourse). The word refers to the study of flags and banners.
Think of 'vexillum' as a flag and '-logy' as the study of something — so vexillology is the study of flags.