Biology and medicine •
Syndromic obesity, excess body fat occurring as part of a syndrome •
Sphincter of Oddi, a muscular valve of the duodenum
Computing •
.so, the top-level Internet domain of Somalia • .so, a filename extension for a
shared object (a dynamic library or module) in Unix and Linux •
Shift Out, an ASCII control character in computing •
Small-outline integrated circuit •
StackOverflow, a programming Q&A site •
Sony's mobile phones in Japan
Mathematics •
SO (complexity), second-order logic in descriptive complexity • Special orthogonal group, a subset of an
orthogonal group •
SO(2), a term used in mathematics, the group of rotations about a fixed point in the Euclidean plane •
SO(3), a term used in mathematics, the group of rotations about a fixed point in three-dimensional Euclidean space •
SO(4), a term used in mathematics, the group of rotations about a fixed point in four-dimensional Euclidean space •
SO(8), a term used in mathematics, the special orthogonal group acting on eight-dimensional Euclidean space • \mathfrak{so}(n), the corresponding
special orthogonal Lie algebra Physics and chemistry •
Sulfur monoxide •
SO(10) (physics), a term used in particle physics, one of the grand unified theories is based on the SO(10) Lie group ==Names==