Pronunciation: [ˈɒd nˈʌmbə] (IPA) 
The phrase "odd number" is spelled with two d's at the end, despite the fact that the pronunciation only calls for one. This is because the root of the word "odd" actually comes from the Old Norse word "oddr," which did contain two d's. Over time, the pronunciation shifted while the spelling remained, resulting in a somewhat irregular spelling for this commonly used phrase. The IPA transcription for "odd number" is ɑd ˈnʌmbər.
"Odd number" refers to a mathematical term representing an integer that cannot be evenly divided by 2, resulting in a remainder of 1. An odd number is any number that is not divisible by 2, and therefore cannot be written in the form of 2n, where n is any integer.
Odd numbers can be identified by observing that they always end with the digits 1, 3, 5, 7, or 9. Examples of odd numbers include 1, 3, 5, 7, 9, 11, 13, 15, and so on, progressing indefinitely. Odd numbers are characterized by the absence of symmetry when divided by 2, which makes them stand out from their counterparts, known as even numbers.
In addition, odd numbers possess distinct properties in mathematical operations. When two odd numbers are added together, the result is always an even number. Similarly, the product of two odd numbers is always odd. Odd numbers also have special significance in geometry, particularly in polygonal shapes, as the inner angles of regular polygons with odd numbers of sides can be evenly divided among the vertices.
Overall, an odd number is a type of whole number that deviates from the regular division by 2, leaving a remainder of 1. This concept plays a crucial role in numerous mathematical fields and serves as a fundamental building block for further mathematical study.
Any number which leaves a remainder on being divided by two.
Etymological and pronouncing dictionary of the English language. By Stormonth, James, Phelp, P. H. Published 1874.
The word "odd" in the context of numbers originates from the Old Norse word "oddr", meaning "point of a weapon". It is believed that the term was adopted into the English language during the Middle English period from the Old Norse language. The concept of an "odd number" being one that is not divisible into pairs, or having a remainder when divided by 2, likely came about due to the perception that such numbers were irregular or unusual, similar to the way a pointed weapon stands out.
