What is the key structural difference between a spiral galaxy (S) and a Lenticular galaxy (S0)?

Answer

Lenticular galaxies lack any discernible spiral arm structure

Lenticular galaxies (S0) share the prominent bulge and flat disk structure of spirals but are distinguished by their absence of spiral arms, implying they have largely ceased major star formation due to a lack of cold gas and dust.

What is the key structural difference between a spiral galaxy (S) and a Lenticular galaxy (S0)?
Spaceclassificationgalaxyastronomy