The laboratory confirmed that the sample was an elementary substance composed solely of hydrogen molecules.

Although his speech wandered through many topics, the sum and substance of his message was a call for unity.

Scientists detected trace amounts of a polyfluoroalkyl substance in the river sediment.

Researchers found traces of a perfluoroalkyl substance in the local water supply after the chemical plant leak.

Don't take the shadow for the substance when assessing someone's character based on a few public appearances.