The second most common word in English is ‘AND’ which is usually a conjunction. It’s also used in complex adverbial phrases:
and so on (A2 in the English Vocabulary Profile EVP)
I need you to help me with my bags and so on.
Also, note that ‘and so forth‘ is not listed in the EVP, but is listed in OXFORD at B1:
I‘ve had ample opportunity to observe Browning and adopt his physical presence, study his mannerisms, and so on and so forth.
TIME AND AGAIN (unlisted in the EVP)
I‘ve told you fellas time and again, this haka won’t work until you get the first action right!
BY AND LARGE (C1)
The men who work for PointCorp, the men you dishonour by calling them mercenaries are,
by and large, retired American military personnel.
BY AND BY (unlisted)
Once and for all (C2)
THROUGH THICK AND THIN (C2)
EVP:
If you support or stay with someone through thick and thin, you always support or stay with them in easy and difficult situations.
BY FAR AND AWAY (unlisted)
‘and’ is also used in interjections:
low and behold (unlisted)
in locative adverbial phrases:
to and fro (unlisted)
and of course in proper names.