Second fundamental form
Definition
Let be a manifold embedded in . the second fundamental form on is the map defined as follows:
where si the Levi-Civita connection of and is the Levi-Civita connection on .
Let  be a manifold embedded in 
. the second fundamental form on 
 is the map 
 defined as follows:
where  si the Levi-Civita connection of 
 and 
 is the Levi-Civita connection on 
.