tube

A hollow cylinder, especially one that conveys a fluid or functions as a passage.

An organic structure having the shape or function of a tube; a duct.

A small flexible cylindrical container sealed at one end and having a screw cap at the other, for pigments, toothpaste, or other pastelike substances.

The cylindrical part of a wind instrument.

An electron tube.

A vacuum tube.

The lower, cylindrical part of a gamopetalous corolla or a gamosepalous calyx.