(physiology) The parts of an animal body comprising the heart, blood vessels (arteries, veins, and capillaries), and blood, which circulate the blood around the body.

In Latin, the three perfect tenses: perfect, future perfect, and pluperfect or past perfect, as contrasted with the present system: present, future, and imperfect. A verb in the perfect system indicates an action that has completed.

In Latin, the three simple tenses: present, future, and imperfect, as contrasted with the perfect system, the three perfect tenses: perfect, future perfect, and pluperfect. Verbs in the present system tend to indicate an action that has not completed.

Any data processing system, either manual or computerized. / Any telecommunications system whose primary function is to transmit and/or display data.

(anatomy) The system of osteons in compact bone

Any assemblage of equipment used to generate, store and distribute electrical power on board a satellite or spacecraft

(medicine) A blood group system, the second most important after the ABO system, and important in human blood transfusion, whereby blood types are classified according to the presence ("positive") or absence ("negative") of potentially over 50 antigens, of which the most commonly referenced is RhD.

(computing) The tool used by an operating system (OS) to administrate addition, removal and upgrade of software applications. Examples of package management systems on different OSes are: Linux: RPM; Solaris: pkgadd; HP-UX: SD-UX; Debian: apt-get; Win32: Windows Installer.

A communication system in which multiple users share a common channel in a way that can lead to conflicts.

(computing) Synonym of issue tracking system