The letters "f" and "g" are the sixth and seventh letters of the English alphabet, respectively. In the context of phonetics, "f" represents a voiceless labiodental fricative sound, as in the word fish, while "g" represents a voiced velar plosive sound, as in the word goat. In mathematics, "f" and "g" are often used to denote functions. A function is a relation that assigns each input exactly one output. For example, if f(x) represents a function that doubles its input, then f(2) would equal 4. Similarly, g(x) could represent another function, such as one that adds three to its input.