bases

Bases in chemistry are substances that participate in reactions by accepting protons or donating electron pairs. The Arrhenius definition characterizes bases as compounds that increase hydroxide ion concentration in water, while the Bronsted-Lowry definition treats bases as proton acceptors. Common bases include hydroxides (such as sodium hydroxide), ammonia, and carbonates. Bases typically have a pH above 7, feel slippery, and react with acids in neutralization reactions to form salts and water. Strength varies: strong bases dissociate completely in solution, whereas weak bases do not.

Mathematics and computer science use the term base in different senses. A numeral base, or radix, defines how numbers are represented, with base-10 and base-2 as familiar examples. Digits range from 0 to base-1, and a digit's position determines its weight in powers of the base. In linear algebra, a basis of a vector space is a set of vectors that are linearly independent and span the space; every vector can be uniquely expressed as a linear combination of basis vectors. The size of a basis equals the space's dimension.

In genetics, nucleotide bases in DNA are adenine, cytosine, guanine, and thymine; RNA uses adenine, cytosine, guanine, and uracil. Bases pair across the double helix: A pairs with T (or U in RNA) and C pairs with G, stabilized by hydrogen bonds. The sequence of bases encodes genetic information and directs cellular processes.

In sports, bases are the four markers on a baseball diamond that runners must touch to score. The order is first base, second base, third base, and home plate. A team advances runners on hits, walks, and other plays, while defensive teams try to prevent advancement and tag runners out.