Al - Muttasil
a hadith with a continuous chain of narrators (isnad) without any gaps or missing links. Each narrator heard the hadith directly from the one before them.
Al- Musnad
a hadith that has a fully connected chain of narrators that leads all the way back to the Prophet Muhammad (saw). It is also associated with books that collect these types of narrations.
Al-Mu’an’an
a hadith where the narrators use the term (" ‘an ” meaning "from") in the isnad, as in "So-and-so narrated from so-and-so." But, it is unclear whether they directly heard it from the person mentioned or not.
Al-Muannan
A hadith where the narrators use the term (“ an ” meaning "that"), as in "So-and-so said that the Prophet (saw) said..." Its continuity depends on whether the narrators are known to have met and heard directly.
Al-Mazid fi Muttasil al-Asanid
a hadith where additional narrators or details were inserted into a connected chain of narrators. Scholars investigate whether the addition is authentic or an error by comparing other chains.