This one might seem obvious, but pronounce both words consecutively and see how close to one another they really are.

At issue is that pesky “g,” which most of us put slightly less emphasis on when saying “singer” than we do when saying “finger” — the hard g is a bit more prominent there, isn’t it? But maybe that’s splitting hairs. After all, the words differ by just one letter and have the same vowel sounds. The more you say one word after another in quick succession, though, the less sure you might become.