1. A theory, this being a termination of words denoting theory.

Nuttall's Standard dictionary of the English language By Nuttall, P.Austin

• issa,
• itm,
• isel,
• isi,
• sysm,
• isalm,
• iium,
• isna,
• isaw,
• raism,
• isam,
• astm,
• gsm,
• ise,
• scism,
• isl,
• isu,
• isil,
• isn,
• esme

• ISN,
• I'm,
• i's,
• ISOM,
• Im-,
• is,
• -ist,
• ISON,
• Isham.

The adjective form of the word "ism" is "istic".

The plural of the "ism" can be the "isms".

The singular of the "ism" can be the "ism".