a bodily passage or tube lined with epithelial cells and conveying a secretion or other substance; "the tear duct was obstructed"; "the alimentary canal"; "poison is released through a channel in the snake's fangs"
a continuous tube formed by a row of elongated cells lacking intervening end walls
the process of ionizing; the formation of ions by separating atoms or molecules or radicals or by adding or subtracting electrons from atoms by strong electric fields in a gas
the condition of being dissociated into ions (as by heat or radiation or chemical reaction or electrical discharge); "the ionization of a gas"
any of the more than 100 known substances (of which 92 occur naturally) that cannot be separated into simpler substances and that singly or in combination constitute all matter
a swinging or sliding barrier that will close the entrance to a room or building or vehicle; "he knocked on the door"; "he slammed the door as he left"
a room that is entered via a door; "his office is the third door down the hall on the left"
a structure where people live or work (usually ordered along a street or road); "the office next door"; "they live two doors up the street from us"
anything providing a means of access (or escape); "we closed the door to Haitian immigrants"; "education is the door to success"