Basic Guidelines For English Spellings
READ THESE ARTICLES
1(forming nouns) in collective numerals.
2(forming nouns) in names of females in classical mythology.
3(forming nouns) in names of poems and similar compositions.
4(forming nouns) in names of members of some taxonomic groupings.
From the Greek ending -as, -ad-.
Forming nouns such as ballad, salad.
From French -ade.