I've been studying Q codes but keep hearing other abbreviations on CW that aren't Q codes. Things like 73, CU, FB, OM, ES and others. Are these standardized or just informal ham slang?

I found a reference that says 73 means "best regards" but I'm hearing it used almost like "goodbye." Also seeing things like "best 73s" which seems redundant if 73 already means best regards?

Can someone explain the most common non-Q code abbreviations and proper usage?

73 is "best regards" and yes, "best 73s" is redundant but commonly used anyway. CU is "see you," FB is "fine business" (meaning good/excellent), OM is "old man" (friend), and ES is "and." These came from telegraph days when every character saved time and money.

Don't forget DE (from/this is), CQ (calling any station), and SK (end of contact). Also 88 for "love and kisses" when signing with YLs. The telegraph operators developed these to speed up transmission, and we've inherited this efficient shorthand.

I use these on phone too! Saying "73" instead of "best regards" is just ham tradition now. GA/GM/GE for good afternoon/morning/evening are handy. Even though we're not tapping keys anymore, these abbreviations are part of our ham culture and make communication more efficient.