Reducing the concentration of a chemical

Stock dilution, the result of new shares of stock being issued by a company, thereby diminishing the percent ownership represented by previously existing shares.

Trademark dilution, a type of unlawful trademark use outside of the relevant market

"Stock dilution" could also refer to a method of preparing soup from stock

Dilution gene, a gene that lightens the coat color of certain living things

Dilution (equation), an equation to calculate the rate a gas dilutes