(1):

(n.) The act of uniting chemically with a solid substance or in a solid form; reduction to a non-volatile condition; - said of gaseous elements.

(2):

(n.) The act or process of ceasing to be fluid and becoming firm.

(3):

(n.) A state of resistance to evaporation or volatilization by heat; - said of metals.

(4):

(n.) The act of fixing, or the state of being fixed.