ADD — meanings: Attention Deficit Disorder, add (verb), addition, and abbreviations

Medical meaning

In informal speech, ADD has long been used to mean Attention Deficit Disorder, a description of substantial inattentive behaviour that can affect school, work and daily life. Contemporary diagnostic systems generally use the term attention-deficit/hyperactivity disorder (ADHD) and recognise an inattentive presentation among its subtypes. Many people still use "ADD" colloquially to refer specifically to the predominantly inattentive form, but clinicians and technical writing typically use the modern diagnostic terminology.

Verb and arithmetic operation

As a verb, "to add" means to join, attach, increase or include. In everyday contexts it covers acts such as adding an ingredient, adding a comment to a document, or adding items to a list. In mathematics, addition is an elementary binary operation that combines quantities to produce a sum; for ordinary numbers it satisfies familiar properties such as commutativity and associativity, and the concept generalises in algebraic structures and computing.

Computing, codes and abbreviations

In computing and programming, "add" commonly names functions or methods that insert elements into collections (for example, list.add(item)), and it is the mnemonic for an assembly instruction that increments a register. Outside computing, the three letters may appear as an abbreviated form in notes (for example, "add." to indicate additional information or an address) and as codes or acronyms: one widely known code is the IATA airport code "ADD" for Addis Ababa Bole International Airport in Ethiopia.

History, usage and style guidance

• Etymology: The verb derives ultimately from Latin addere through Old French and Middle English forms meaning to "give to" or "bring to."
• Terminology: Use the precise medical term (ADHD, inattentive presentation) in clinical or technical writing; "ADD" persists in informal contexts.
• Disambiguation: Capitalisation, surrounding words and domain (medicine, mathematics, computing, travel) normally make the intended meaning clear; when ambiguity matters, spell out the sense (for example, "addition," "to add," or "ADHD, inattentive presentation").

Because the short sequence "ADD" spans distinct fields, writers should provide sufficient context or choose more specific wording to avoid misunderstanding.