Mathematical language can be difficult to understand for beginners because even common terms, such as "or" and "only", have a more precise meaning than they have in everyday speech, and other terms such as "open" and "field" refer to specific mathematical ideas, not covered by their laymen's meanings. Mathematical language also includes many technical terms such as "homeomorphism" and "integrable" that have no meaning outside of mathematics. Additionally, shorthand phrases such as "iff" for "if and only if" belong to mathematical jargon. There is a reason for special notation and technical vocabulary: mathematics requires more precision than everyday speech. Mathematicians refer to this precision of language and logic as "rigor".