OSB 1/2 4 ft. x 8 ft. Oriented Strand Board

1 (one, unit, unity) is a number representing a single or the only entity. 1 is also a numerical digit and represents a single unit of counting or measurement. For example, a line segment of unit length is a line segment of length 1. In conventions of sign where zero is considered neither positive nor negative, 1 is the first and smallest positive integer. It is also sometimes considered the first of the infinite sequence of natural numbers, followed by 2, although by other definitions 1 is the second natural number, following 0.

The fundamental mathematical property of 1 is to be a multiplicative identity, meaning that any number multiplied by 1 equals the same number. Most if not all properties of 1 can be deduced from this. In advanced mathematics, a multiplicative identity is often denoted 1, even if it is not a number. 1 is by convention not considered a prime number; this was not universally accepted until the mid-20th century. Additionally, 1 is the smallest possible difference between two distinct natural numbers.

The unique mathematical properties of the number have led to its unique uses in other fields, ranging from science to sports. It commonly denotes the first, leading, or top thing in a group.

2 (two) is a number, numeral and digit. It is the natural number following 1 and preceding 3. It is the smallest and only even prime number. Because it forms the basis of a duality, it has religious and spiritual significance in many cultures.

4 (four) is a number, numeral and digit. It is the natural number following 3 and preceding 5. It is a square number, the smallest semiprime and composite number, and is considered unlucky in many East Asian cultures.

OSB may refer to:

• Orlando Solar Bears
• OSB, Amtrak station code for the Old Saybrook station in Connecticut, United States
• Oklahoma School for the Blind
• OneSavings Bank plc, a UK registered bank that operates under the trade name Kent Reliance
• Open Source Business Alliance, sometimes known as OSB Alliance
• Operation Smiling Buddha, code name for India's first successful test explosion of a nuclear bomb (1974)
• Oberstabsbootsmann, the highest non-commissioned officer rank in the German Navy
• Operation Sovereign Borders, Australian border security operation
• Oracle Service Bus, a software communication system made by Oracle Inc.
• Oregon State Bar, public body that regulates the legal profession in Oregon, United States
• Oriented strand board, an engineered wood
• Orquestra Sinfônica Brasileira, the Portuguese name of the Brazilian Symphony Orchestra

X, or x, is the twenty-fourth letter of the Latin alphabet, used in the modern English alphabet, the alphabets of other western European languages and others worldwide. Its name in English is ex (pronounced ), plural exes.