In Nitherian culture, the village elders had a special role as advisors and decision-makers. Usually this was limited to local decisions, but elders were also important at the national level: kings and queens would maintain a council of elders, sent from various villages around the kingdom. One of the powers this body had was that they had to approve any proposed marriages by members of the royal family. Hence the following sentence:
Lane moseeleshinyesho nizhimishon.
I’ve phrased this with an initial “but” to give it some implied discourse context. This is a sentence that might appear in a passage describing who wanted to get married and why. Then when we get to “But the council of elders rejected the marriage”, the marriage itself has already been introduced and is old information. To indicate this, the speaker has incorporated the word shinye “marriage” as a suffix of the verb seelyo “to reject”.
The corresponding sentence with shinye as a separate word (Moseelyochi shinye nizhimishon) would only be used if this particular marriage was new to the conversation and the speaker wanted to go on to say more about it. In English it would likely be rendered with the indefinite article: “The council of elders rejected a marriage”.