(1):

(n.) The act or process of reducing, by depression of temperature or increase of pressure, etc., to another and denser form, as gas to the condition of a liquid or steam to water.

(2):

(n.) A rearrangement or concentration of the different constituents of one or more substances into a distinct and definite compound of greater complexity and molecular weight, often resulting in an increase of density, as the condensation of oxygen into ozone, or of acetone into mesitylene.

(3):

(n.) The act or process of condensing or of being condensed; the state of being condensed.