Complex sentence: Verisimilitude, in a narrow sense, is the acceptable level of likeness, similarity, or semblance (as opposed to exact faithfulness) of a work of fiction or narrative to reality, or to the truth.
Split into simpler sentences: Verisimilitude, in a narrow sense, is lifelikeness in a work of fiction. This means the acceptable similarity, likeness, or semblance (but not necessarily exact faithfulness) of the work to reality, or to the truth.