IPA: /ˈfɒloʊˌʌp/
KK: /ˈfɑloʊˌʌp/
A followup is an action or communication that occurs after an initial event or meeting, often to check on progress or to provide additional information.
After the meeting, I sent a followup email to summarize our discussion.
Follow-up → It is formed from "follow" (from Old English "fōlgan", meaning to go after or pursue) and "up" (meaning to a higher position or level). The word "follow-up" refers to the act of pursuing or checking on something after an initial action or event.
Think of going 'after' something ('follow') and then taking it to a 'higher level' ('up') — that's what a follow-up means.
No commonly confused words.