Judging the ripeness of fruit is a very tricky thing. Squeeze, sniff and eyeball every fruit in the supermarket, and you still may be disappointed when you bite in. Fortunately, someone thought of a more exact and scientific way to measure fruit’s ripeness: Adolf Brix, creator of today’s Word of the Day.

The Brix Scale measures the sweetness of a fruit, since fruit’s sugar concentration increases as it ripens. How is this measured? With the help of a handy refractometer—an instrument that looks like a small telescope and measures how light refracts in a drop of fruit juice. Different fruits have different Brix concentrations, but, generally, the higher the Brix number, the sweeter the fruit. A good Brix number can range from 12°Bx (good for avocadoes and tomatoes) to as high as 30°Bx (good for a fig). Some supermarkets have started including Brix measurements on their labels, but, until this practice becomes widespread, you may have to invest in a refractometer.

Use today’s Word of the Day: Sweet Avocado Ice Pops