(anatomy) A system of organs for the purpose of digesting food.

(anatomy) The skin, feathers and other outer coverings of an animal.

(taxonomy) A coherent system of taxonomic judgements on circumscription and placement of the considered taxa. A taxonomic system is restricted to a large but limited part of the living world.

A system used to determine the result of an election based on the preferences expressed by voters.

feudalism

(physiology) A control system of ductless glands that secrete hormones which circulate via the bloodstream to affect cells within specific organs.

A physical system for organizing documents, as in a library or office. / (computing) A method of organizing blocks of data on a storage device into files and directories.

(geometry, mathematical analysis) A method of representing the position of any individual point in a space of given dimensionality as a tuple of numerical coordinates.

(anatomy) In mammals, including humans, a network of lymph vessels and lymph nodes that transport fluid, fats, proteins, and lymphocytes to the bloodstream as lymph, and remove microorganisms and other debris from tissues.

(computing) A system allowing hardware and software from different manufacturers to be used together seamlessly. / (physics) A system that can exchange both matter and energy with its surroundings.