Septuagenarian? No can understand...

I read Bernama news Singapore City-train Service Disrupted today and stumbled upon the word "septuagenarian". I am quite familiar to the word thanks to my previous lecturer. However my poor girlfriend didn't understand the term. So, here I'm doing her (and you all) a service, trying to list all the weird words and their definitions.

1. sexagenarian: someone whose age is in the 60's (60-69);
2. septuagenarian: someone whose age is in the 70's (70-79);
3. octogenarian: someone whose age is in the 80's (80-89);
4. nonagenarian: someone whose age is in the 90's (90-99);
5. centenarian: someone who is at least 100 years old.
6. supercentenarian (sometimes hyphenated as super-centenarian): someone who has reached the age of 110 years. [Wiki]
7. "pentagenarian": someone whose age is in the 50's (50-59).

I hope it helps. Cheers! ;)