IPA: /ˈɒnlaɪn/
KK: /ˈɑnˌlaɪn/
Relating to or available through a computer or network, especially the Internet.
I prefer to take online courses because they are more flexible.
Online → It is formed from "on" (meaning in a state of) and "line" (from Latin "linea", meaning a line or string). The word "online" refers to being in a state of connection through a line or network.
Think of being 'in a state of' ('on') connected through a 'line' — that's what online means.