What is meant by the Three, Five, Six, or Seven Narrators, and are the narrators of hadith limited to them only? And who are they?

This answer clarifies the meanings of some common terms found in Hadith books, which are:

Ibn Taymiyyah al-Jadd in "Muntaqa al-Akhbar": "Narrated by the Five": Ahmad, Abu Dawud, An-Nasa'i, At-Tirmidhi, and Ibn Majah. "Narrated by the Group" (al-Jama'ah): The Five in addition to the two Sahih collections (Bukhari and Muslim). "The Seven" (according to al-Muhibb At-Tabari, as mentioned by Ash-Shawkani and Ibn Hajar): Refers to what was narrated by the Group (al-Jama'ah).

Ibn Hajar in "Bulugh al-Maram": "The Seven": What was narrated by Imam Ahmad, the two Sahih collections (Bukhari and Muslim), and the four Sunan books (Abu Dawud, At-Tirmidhi, An-Nasa'i, and Ibn Majah). "The Six": The Seven excluding Musnad Ahmad. "The Five": The Sunan books and the Musnad (Abu Dawud, At-Tirmidhi, An-Nasa'i, Ibn Majah, and Ahmad). "The Three": Sunan Abu Dawud, At-Tirmidhi, and An-Nasa'i.

As-Suyuti in "Al-Jami' As-Saghir": Symbol (3): What was narrated by Abu Dawud, An-Nasa'i, and At-Tirmidhi.