The letter "H" is the eighth letter of the English alphabet. It is a consonant and is often used to represent the sound made by exhaling air, as in words like "hat" and "house." In the phonetic alphabet, "H" is pronounced as "aitch." In chemistry, "H" stands for hydrogen, the simplest and most abundant element in the universe. It has one proton and one electron, making it essential for the formation of water and organic compounds. Hydrogen plays a crucial role in various chemical reactions and is a key component in energy production.