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Have you checked under the sink recently or did this come out of nowhere?
Most of the time it's the seals degrading around the pipes. First check the connections under the sink - where the pipes connect - because the nuts loosen over time and water leaks out. The rubber or silicone seals dry out and crack after a few years, especially if the area is exposed to constant moisture. Another common source is the trap itself cracking or the seals failing. You can try tightening the nuts with an adjustable wrench, but be careful not to overtighten - that can crack the PVC piping.
If it's not the connections, you've still got to check the main drain line. It can have a small hole or crack, especially if it's old or corroded copper. The easiest thing is to soak up the water, let the area dry completely, then watch for a few hours to see exactly where the water comes back. That'll let you pinpoint the source precisely. If it's just a dead seal, you can replace that yourself with cheap parts from the hardware store. But if it's a crack in the piping itself, you're probably going to need to get the section replaced or call someone in.
In my case it was super sneaky because the leak wasn't coming straight from the seal but from the drain pipe that had gotten slightly cracked on the inside - hard to spot at first glance. What people often forget to check is whether the water only drips when you're using the sink or if it's leaking constantly, because that completely changes the diagnosis. If it's constant, check the cold/hot water supply lines; if it's mostly dripping while you're running water, it's probably the drain system.
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