(chemistry) a reaction in which one functional group is replaced with another

(chemistry) in aliphatic organic chemistry, a form of substitution reaction in which the leaving functional group is replaced with a nucleophile

(chemistry) in aromatic organic chemistry, a form of substitution reaction in which the leaving functional group (normally hydrogen) is replaced with an electrophile

A document in which the party to a lawsuit states that his/her attorney of record is being substituted for by another attorney or by the party acting for himself/herself (in propria persona).

(cryptography) A method of encryption by which units of plaintext are substituted with ciphertext according to a regular system; the "units" may be single letters (the most common), pairs of letters, triplets of letters, mixtures of the above, and so forth. The receiver deciphers the text by performing an inverse substitution.

A substitution cipher

A substance that tastes salty but contains less sodium than table salt (sodium chloride), or none at all.

plural of salt substitute

(soccer) The bench on which the players sit when they are not in action.

(organic chemistry) A system for naming organic compounds in which a functional group is used either as a prefix or a suffix to the name of a parent compound e.g. trinitrotoluene or benzenesulfonic acid