(geology) a cloud of ash emitted during a volcanic eruption

(environmental sciences, hydrology) A notional column of water from the surface to the bottom in a natural setting, notable for the differences in physical and chemical properties at various depths.

hypercolumn

(linear algebra) An n×1 matrix that represents a vector.

A glowing region in a glow discharge between the Faraday dark space and the anode glow.

A half column.

Section of a periodical in which readers' letters are published.

(chiefly UK) A column of a newspaper which contains advertisements relating to lost relatives and friends and other personal matters.

(architecture) A column embedded in a wall and partly projecting from the surface of the wall

A newspaper feature in which questions (typically from anonymous readers who seek advice) are answered by an advice columnist (or agony aunt).