text: However, occurs in many common digraphs, all with their own sound or sounds, particularly , , , , and .is the third-most-commonly used letter in English (after and ) and French, the second most common in Spanish, and the most common in Portuguese.About 8.167% of letters used in English texts tend to be ; the number is around 7.636% in French, 11.525% in Spanish, and 14.634% for Portuguese.Other languages In most languages that use the Latin alphabet, denotes an open unrounded vowel, such as , , or .An exception is Saanich, in which (and the glyph Á) stands for a close-mid front unrounded vowel .Other systems In phonetic and phonemic notation: in the International Phonetic Alphabet, is used for the open front unrounded vowel, is used for the open central unrounded vowel, and is used for the open back unrounded vowel.in X-SAMPA, is used for the open front unrounded vowel and is used for the open back unrounded vowel.Other uses In algebra, the letter a along with various other letters of the alphabet is often used to denote a variable, with various conventional meanings in different areas of mathematics.Moreover, in 1637, René Descartes "invented the convention of representing unknowns in equations by x, y, and z, and knowns by a, b, and c", and this convention is still often followed, especially in elementary algebra.In geometry, capital A, B, C etc.are used to denote segments, lines, rays, etc.A capital A is also typically used as one of the letters to represent an angle in a triangle, the lowercase a representing the side opposite angle A."A" is often used to denote something or someone of a better or more prestigious quality or status: A−, A or A+, the best grade that can be assigned by teachers for students' schoolwork; "A grade" for clean restaurants; A-list celebrities, etc.Such associations can have a motivating effect, as exposure to the letter A has been found to improve performance, when compared with other letters.