Injekcij

Injekcij is a term used in some languages to denote injection, the introduction of a substance into the body, or the mathematical concept known in English as an injective function. In everyday context, it most commonly refers to medical injections performed with a syringe, such as vaccines or medications delivered intramuscularly, subcutaneously, or intravenously. In mathematics, an injection (injective function) is a mapping that preserves distinctness of elements: if x1 ≠ x2, then f(x1) ≠ f(x2).

Medical injections involve delivering a precise dose of a substance using sterile equipment. Procedures emphasize aseptic technique, correct needle size and route, and accurate dosing. The main routes are intramuscular (into a muscle), subcutaneous (into the fatty tissue beneath the skin), and intravenous (into a vein). Preparation includes verifying patient information, checking for allergies, and observing storage requirements for the substance. After administration, patients may be monitored for immediate reactions and instructed on possible local effects at the injection site, such as pain, redness, or swelling. Common indications include vaccination, administration of medications, and rapid systemic delivery when other routes are unsuitable. Side effects range from mild to severe and require medical attention if they occur.

In mathematics, an injection is a one-to-one function: each element of the domain maps to a unique element of the codomain. Equivalently, f(x) = f(y) implies x = y. Injective functions can be non-surjective, meaning not every element of the codomain is the image of the domain. Examples include f(n) = 2n from integers to even integers, which is injective but not surjective.