session, cession

Session or session means a series of meetings or group functions--
The current session of congress began in January.
The musicians stayed on after hours for a jam session.

Cession or cession ( rhymes with session ) means an act or instance of giving something up or yielding something, as in a treaty--
The new treaty calls for the cession of some territory.
They'll never agree to the cession any of their land or territory.

Now that you know that, you can say--
"This session of the treaty negotiations will be about the cession of the disputed territory."

Note--"cession" is a noun ( thing or idea ) form of "cede", meaning to give up--
The other side is demanding that we cede this territory.
Not to be confused with "concede", meaning to give up a point, or to agree that the other party is right about a disputed point--
They may argue all day, and neither will concede the point.
Note # 2--"cessation" is a noun ( thing or idea ),, a form of "cease", meaning to stop. Cessation means an end or stop--
They agree to a cessation of hostilities, and to the terms of the treaty.