I'm looking for additional languages, other than the Slavic ones, which do not have the property English has, i . e either : languages that don't have a word denoting a symmetric relation which is not a symmetric " natural " relation, or languages that have a word denoting another symmetric relation ( i . e . other than " sibling in law " ) which is not a symmetric " natural " relation.
22.
Now, English ( along with almost all of the other well known languages ), has the following-interesting-property : " Sibling-in-law " ( or brother-in-law and sister-in-law-if we consider gender, along with the obvious parallel co-sibling-in-law ) is the "'only "'relation ( between relatives ) in the language, which is a symmetric relation, yet not a symmetric " natural " relation.
23.
Ernst Schr�der in " The Algebra of Logic " consolidated and advanced the work of Boole and Peirce introducing the concept of the reflexive relation, and Alfred Tarski, adhering to Schr�der s notation, introduced further types of relation in his paper " On the Calculus of Relations " published in 1941 where he said We may for instance distinguish certain important categories of relation such as symmetric relations, transitive relations, ordering relations, one-many relations & and one-one relations & .
