If you look at online answers, many say "ya" is like "Oh" as in "Oh Betty, could you hand me that pencil?" You use "Ya" only when addressing someone directly. I think of it as "a very polite 'Hey'," like "Hey Bon, I hope my answer makes sense." But in English "Hey" is optional and a little rude or at least very informal. "Ya" is not optional (or less optional?) and polite. Edit: More research tells me it is more like the "O!" in "O Hamlet, speak no more!" when "O" was used commonly in English to address a person. So think of Shakespeare's English. But while we dropped the polite "O" over time, Arabic retained it's polite "Ya." See https://arabic.desert-sky.net/coll_address.html

keefek means ( How are you?) ya is for calling or grabbing the attention of a specific person. in English, we say "Bon, come here" or "Hi, Bon." or " How are you, Bon?", but in Arabic, we say "Ya Bon, taealaa" or "Hi ya Bon" or " Keefak ya Bon?" I hope this answers your question.

"keefek ya Bon? it just means . how are you ?