IPA: /kʌstəˈmɛrɪli/
KK: /ˈkʌstəmɛrɪli/
In a way that is usual or expected based on tradition or habit.
People customarily greet each other with a handshake at formal events.
Customarily → It is formed from "custom" (from Latin *consuetudo*, meaning habit or practice) and the suffix "-arily" (meaning in a manner relating to). The word "customarily" means in a manner that relates to established habits or practices.
Think of 'custom' as a habit or practice, and remember that 'customarily' means doing something in a habitual way.