<p><strong>Noun</strong></p><ul><li>A colorless, odorless, flammable gas that combines chemically with oxygen to form water: the lightest of the known elements.</li><li>Symbol: H</li><li>Atomic weight: 1.00797</li><li>Density: 0.0899 grams/liter at 0°C and 760 millimeters pressure.</li></ul>