To allay means to calm or reduce something unpleasant, like fear, worry, or pain. When you allay someone's concerns, you help them feel less anxious by giving them good reasons to relax.

Imagine your younger sibling is nervous about their first day at a new school. You might allay their fears by telling them about the fun activities they'll do, the friends they'll make, and how you felt the same way but everything turned out fine. A doctor might allay a patient's anxiety by carefully explaining what will happen during a procedure. A teacher might allay confusion about a complicated assignment by breaking it down into clear steps.

The word suggests gentle soothing rather than a dramatic fix. You allay doubts, you allay suspicions, you allay worries. Think of it like smoothing out wrinkles in fabric: the problem doesn't disappear completely, but it becomes much less troublesome. When a good explanation allays your confusion about a math problem, you feel that relief of understanding replacing uncertainty.