What does "contraction" mean?

Additional senses

1. 2.The act of incurring or becoming subject to, as liabilities, obligation, debts, etc.; the process of becoming subject to; as, the contraction of a disease.
2. 3.Something contracted or abbreviated, as a word or phrase; -- as, plenipo for plenipotentiary; crim. con. for criminal conversation, etc.
3. 4.(Gram.) The shortening of a word, or of two words, by the omission of a letter or letters, or by reducing two or more vowels or syllables to one; as, ne'er for never; can't for can not; don't for do not; it's for it is.
4. 5.A marriage contract. [Obs.] Shak.