How do synonyms best readers to figure out the meanning of unknown words

Synonyms help us connect unknown words with known words. For example, one may not know the meaning of the word "nefarious" when used in this context: "The offense was more nefarious than previously thought." If we replace "nefarious" with "evil" or "wretched" the meaning is more comprehensible to those who don't know the meaning of "nefarious": The offense was more evil (wretched) than previously thought." 
I hope this helps, I used nefarious as a somewhat uncommon term to better illustrate my point, and to explain why we use synonyms to learn new words. Simply put, synonyms bridge us to the unknown using the known as solid ground build from. 

It provides others words the subject might understand.

It depends on what type of third separates the three notes.for example: if you have two mayor thirds is an "aumented chord"if you have two minor thirds is an "diminued chord"if you have one mayor first and then one minor is a "mayor chord"and inverted is a "minor chord"