1. postposition - Noun
2. postposition - Verb
The act of placing after, or the state of being placed after.
A word or particle placed after, or at the end of, another word; -- distinguished from preposition.
Source: Webster's dictionaryA locative postposition expresses an absolutely different meaning to that of an instrumental, so it is evident that both of them are not related whatsoever. Source: Internet
The regular "with" is expressed with the postposition kanssa, thus this form is used in most cases, e.g. suurien laivojensa kanssa "with their big ships". Source: Internet