Abstract:Let $k$ be a field.In this talk we introduces the notions of $n$-serial algebras and $n$-serial coalgebras over $k$ and discuss their properties. Of course, in case $n=1$, $n$-Serial Algebras are cannonical Nakayama algebras, and $n$-serial coalgebras are serial coalgebras. In this talk, we will give some results on 2-series algebras and 2-series coalgebras. Especially, we will introduce sufficient and necessary conditions for an algebra to be a 2-serial algebra or a coalgebra to be a 2-serial coalgebra