odd

Odd is an adjective in English with several related meanings. In everyday use, it describes something unusual, irregular, or not typical. It can refer to a person whose behavior or appearance stands out, or to events that seem out of the ordinary. In amounts or quantities, odd can imply a small, leftover, or approximate portion, as in odd jobs or odds and ends. The term can convey whimsy or peculiarity, rather than a value judgment about quality.

In mathematics, odd has a precise sense. An odd integer is any integer not divisible by 2; equivalently, a number congruent to 1 modulo 2 (examples: 1, 3, 5). Even numbers are those divisible by 2. The concept extends to other areas of math, such as odd functions, where a function f satisfies f(-x) = -f(x). In computing and information theory, odd parity refers to a parity scheme in which the total number of 1-bits is odd, used for error detection.

In everyday language, phrases such as the odd one out, an odd habit, and odds and ends illustrate its flexible usage. The word can carry neutral, humorous, or slightly critical connotations depending on context. The noun form oddity or the noun phrase oddball is used to describe a person or thing notably unusual, with tonal meaning ranging from affectionate to dismissive.