In case other people are wondering why it's "la amistad" rather than "el amistad" (given that it's "el agua" even though agua is feminine), I looked this up, you only switch to using masculine article if the stress is on the first a. If it's on a later syllable then you still use la.
This subject could be studied in depth, but here's something that seems to work here on Dúo: if you mean something in general, English doesn't use the def. art. but Spanish often does. Some examples:
Elephants are big (elephants in general, all elephants). Los elefantes son grandes.
Cigarettes are dangerous (all cigarettes in general). Los cigarrillos son peligrosos.
I believe in friendship (all friendship in general). Creo en la amistad.
I don't like Chinese food (all Chinese food in general). No me gusta la comida china.
This might help with at least this type of sentence.