Serial commas Wikipedia:Manual of Style

mos:serial
mos:oxford
mos:harvard

a serial comma (also known oxford comma or harvard comma) comma used before conjunction (and or or, nor) in list of 3 or more items: phrase ham, chips, , eggs includes serial comma, while ham, chips , eggs omits it. editors may use either convention long each article internally consistent; however, there times when serial comma can create or prevent confusion:

sometimes omitting comma can lead ambiguity:


including comma can cause ambiguity:

in such cases of ambiguity, there 3 ways clarify:

add or remove serial comma.
use paragraph breaks, bullet lists, or numbered paragraphs clarify.
recast sentence (first example above):

to list 4 people: author thanked sinéad o connor, bob marley , parents.
to list 2 people: author thanked bob marley , sinéad o connor, parents.

clearer: author thanked parents, bob marley , sinéad o connor.
or (the commas here set off non-restrictive appositives): author thanked father, bob marley, , mother, sinéad o connor.




recast sentence (second example above):

to list 2 people: author thanked bob marley , mother, sinéad o connor.
to list 3 people: author thanked mother, bob marley, , sinéad o connor.

the clarity of last example depends on reader knowing marley male , cannot mother. if change example slightly, ambiguous statement: author thanked mother, irish president mary mcaleese, , sinéad o connor.
clearer: author thanked bob marley, sinéad o connor, , mother; or author thanked irish president mary mcaleese, sinéad o connor, , mother.