Hatcher uses the words "path-component" and "component" without giving their definition. The first occurrence of "path-component" is on p. 19, exercise 12. The first occurrence of "component" is on p. 6, example 0.2.
I think "path-component" means "path-connected component". But what is a "component" of a topological space? He seems to use it to mean a $k$-cell, for any $k$. Is this the definition?
Thank you for your help.