congress (i.e., 2-year time-frame)

When referring to a time-period (e.g., the 114th Congress which convened on January 6, 2015) rather than the legislative branch generally, a Congress is the national legislature in office (for approximately two years). It begins with the convening of a new Congress comprised of members elected in the most-recent election and ends with the adjournment sine die of the legislature (typically after a new election has occurred).