There are different Usages of the letter G.
1. the seventh letter of the English alphabet
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
This letter denotes the next after H in a set of items, categories, sizes, etc. e.g. It also denotes the seventh of seven or more hypothetical people or things.
2. Music Chess
In Music, it denotes the fifth note in the diatonic scale of C major.. And, in Chess, it denotes the seventh file from the left on the board, as viewed from White's side of the board.
G = Grand that equals to a thousand dollars, a dialect approach in North America. g = gram a metric unit of mass as in Kilogram. 1000g = 1Kg. g = acceleration due to gravity = 9.8 meters per second square. Besides, G letter of English Alphabet is used in Gabon a country located on the West Coast of Africa, as International Vehicle Registration.
G = Gauss, a unit of magnetic induction named after Karl Friedrich Gauss, that equals to one ten-thousandth of one tesla. G = Gibb's Free Energy named after J W Gibbs which is a thermodynamic quantity that equals to the enthalpy minus the product of entropy and the absolute temperature. G = Gravitational Constant = 6.67 × 10−11 N m2 kg−2 as in Newton's Law of Gravitation relating Gravity to the masses and separation of particles, F = G. Mm/r2
G-Spot is also called the Gräfenberg spot and is characterized as an erogenous area of the female secondary sexual organ vagina that, when stimulated, may lead to strong sexual arousal. Its existence is still a debate.
The most Common Noun which is used to learn this letter at the Nursery level is Girl; G for Girl.