The word Sayyid can be translated as master, chief or leader. It is permissible and praiseworthy to give this title to Prophets, Sahaba and the family of the Prophet Muhammad ﷺ.
You will often hear and see the title Sayiduna (our master) or Sayyidi (my master) being placed before the name of the Messenger of Allah ﷺ. He ﷺ has said in a famous Hadith:
I am the Sayyid (master) of the children of Adam, and it is no boast.
Ibn Majah
The term can also be used for the Ahl al-Bait (family of the Prophet ﷺ). The Messenger of Allah ﷺ said to his daughter Sayidah Fatima (may Allah be pleased with her):
O Fatima, does it not satisfy you that you will be the Sayyidah (leader) of the women of paradise?
Bukhari
The Messenger of Allah ﷺ once said about his grandson, Imam al-Hasan:
Indeed this son of mine is a Sayyid (chief).
Bukhari
The descendants of the Prophet ﷺ are usually referred to as Sayyid also. In some countries they are given the title Shareef.
The term Sayyid can also be used for the Sahaba. The Messenger of Allah ﷺ once told the people to stand up for the great companion, Sa’ad ibn Muadh. He ﷺ said:
Stand up for your Sayyid (master)!
Bukhari and Muslim
Sayiduna Umar used to say about Sayiduna Abu Bakr and Sayiduna Bilal:
Abu Bakr is our Sayyid (master) and he emancipated our Sayyid (master).
Bukhari
The second Sayyid is in reference to Bilal. This is because he was a slave until Abu Bakr freed him.
Sayyid can also be used for scholars and other respectable Muslims, hence why it is common to see the great Ulema of the past being referred to with this title.
Orthodox Muslim 