Active attentiveness means staying mentally present with someone, picking up their words, tone, and situation instead of just hearing them. A coworker says, I can take the weekend shift, but sounds tired. You notice and ask, You sound worn out. Are you sure?
Your manager lists three deadlines and you need only one detail. You also catch that she flagged the budget line as a guess, so you later ask, Was that cost estimate firm, or should we double-check it? You were tracking the whole message, not just the part assigned to you.
A caller says, Everything's fine, but pauses before the words. You hold the silence and ask gently, Is there something you'd rather talk about? Hearing alone would miss the pause; active attentiveness does not.
Attentiveness versus active listening
Attentiveness is the paying-attention part. Active listening is the whole process: it includes attentiveness plus what you do next, like nodding, giving short verbal feedback, and checking that you understood. So attentiveness is one ingredient; active listening is the finished dish.
That said, sources vary. Some writers use the terms loosely or even interchangeably, so treat this split as one common way of framing it, not a universal rule.