Nothing is a concept that describes the lack or absence of anything at all. Colloquially, the concept is often used to indicate the lack of anything relevant or significant, or to describe a particularly unimpressive thing, event, or object. It is contrasted with something and everything. In some Eastern philosophies, the concept of "nothingness" is characterized by an egoless state of being in which one fully realizes one's own small part in the cosmos.
Clauses can often be restated to avoid the appearance that "nothing" possesses an attribute. For example, the sentence "There is nothing in the basement" can be restated as "There is not one thing in the basement". "Nothing is missing" can be restated as "everything is present". Conversely, many fallacious conclusions follow from treating "nothing" as a noun.
Modern logic made it possible to articulate these points coherently as intended, and many philosophers hold that the word "nothing" does not function as a noun, as there is no object that it refers to. There remain various opposing views, however—for example, that our understanding of the world rests essentially on noticing absences and lacks as well as presences, and that "nothing" and related words serve to indicate these.
The understanding of 'nothing' varies widely between cultures, especially between Western and Eastern cultures and philosophical traditions. For instance, Shunyata (emptiness), unlike "nothingness", is considered to be a state of mind in some forms of Buddhism (see Nirvana, mu, and Bodhi). Achieving 'nothing' as a state of mind in this tradition allows one to be totally focused on a thought or activity at a level of intensity that they would not be able to achieve if they were consciously thinking. A classic example of this is an archer attempting to erase his mind and clear his thoughts in order to better focus on his shot. Existentialism and Martin Heidegger have brought these two understandings closer together.
The Kyoto school handles the concept of nothingness as well.
In physics, the word nothing is not used in any technical sense either. A region of space is called a vacuum if it does not contain any matter, though it can contain physical fields. In fact, it is practically impossible to construct a region of space that contains no matter or fields, since gravity cannot be blocked and all objects at a non-zero temperature radiate electromagnetically. However, even if such a region existed, it would still not be referred to as "nothing", since it has properties and a measurable existence as part of the quantum-mechanical vacuum.
In computing, "nothing" (in VB.Net), or "null" (in Java, C#, and others), can be a keyword used to represent an unassigned variable, a pointer that does not point to any particular memory address, or a reference that does not refer to a specific object. Similarly, null is used in SQL as a symbolic representation of the absence of data. This meta-data usage of null is different from the unprintable ASCII and unicode null character, which has a numerical value of zero—although this is different from the ASCII character for zero ("0"). The ASCII blank character (" ") is not the same as an empty string (""), which is itself sometimes confused with the null pointer in languages such as C. Most forms of assembly language have a no-operation (NOP) instruction (often with a numerical value of zero)—that is, a command to do nothing, which can prove useful for blanking out areas of problem code.