Final answer:
The Year of Sorrow was a pivotal time in Prophet Muhammad's life, characterized by personal losses and persecution, leading to the hijra to Medina, which marks the beginning of the Islamic calendar.
Step-by-step explanation:
The Year of Sorrow refers to a period in the Prophet Muhammad's life marked by personal losses and escalating persecution. This year is particularly significant because it encompasses the death of his supportive wife, Khadija, and his uncle and protector, Abu Talib. Following these events, Muhammad faced increased hostility from the polytheistic Meccan community, which eventually led to his hijra, or emigration, to the city of Medina in 622 CE.
This migration marked the start of a new era for Islam as Muhammad's followers solidified their community and expanded their influence. The difficulties Muhammad faced during the Year of Sorrow also highlight the resilience and steadfastness of his prophetic mission. It exemplifies the transition of Islam from a small group of followers in Mecca to a community united by faith under the leadership of Muhammad in Medina, where it could grow into a significant socio-political force.