Square and Compasses any Masonic symbol) that is used by Freemasonry as a whole. In many English speaking countries, the Square and Compasses are depicted with the letter "G" in the center. The letter has multiple meanings, representing different words depending on the context in which it is discussed. The most common is that the "G" stands for Geometry, and is to remind Masons that Geometry and Freemasonry are synonymous terms described as being the "noblest of sciences", and "the basis upon which the superstructure of Freemasonry, and everything in existence in the entire universe is erected. In this context it can also
G-structure on a manifold condition. Without the corresponding integrability condition, the structure is instead called an "almost" structure, as in an almost complex structure, an almost symplectic structure, or an almost Kähler structure. Specifically, a symplectic manifold structure is a stronger concept than a "G"-structure for the symplectic group. A symplectic structure on a manifold is a two-form "ω" on "M" that is non-degenerate (which is an formula_38-structure, or almost symplectic structure), "together with" the extra condition that d"ω" = 0; this latter is called an integrability condition. Similarly, foliations correspond to "G"-structures coming from block matrices, together with integrability conditions so that the