I say "okay" quite often, both when speaking English and my native language, which is Swedish. Here are some examples of how I use it:
To describe something, replacing words like fine, good enough, so-so or alright:
"It was... okay."
To show that one agrees, understands or accepts:
"OK"
To console someone when they feel guilty or sad:
"It's okay"
What can I say in Esperanto?