A starship is a manned spacecraft that is capable of viable interstellar travel via the ability to transport and support a crew across interstellar distances in a reasonable time. A starship accomplishes this via the employment of some form of faster-than-light spacecraft propulsion technology, such as warp drive.
In the Terran Empire, during the 23rd century, starships were identified exclusively as vessels operated by Starfleet. Within the Empire, starships were viewed as the role of enforcer of law, as starship captains were given a certain level of authority in the region they patrolled.
Design is also a factor in defining a starship. Likewise, a starship can be identified on sensors by power utilization curve, as a vessel utilizing 100% power has the ability to skew sensor readings.
By the mid-24th century, the exclusiveness of term starship would essentially fall out of use, and would be redefined as a term interchangeable with spaceship and spacecraft.