The Oxford Thesaurus An A-Z Dictionary of Synonyms INTRO ...

absolutely, Colloq for sure: I know for a certainty that I
cannot fly.
certify v. 1 confirm, attest (to), verify, testify (to), affirm, aver,
asseverate, corroborate, substantiate, endorse, guarantee,
warrant; swear (to), bear witness (to), vouchsafe, vouch (for):
I will certify the accuracy of the report. She certified that
she was the owner of the car. 2 declare, classify, establish,
confirm: The magistrate certified the man insane.
3.3 chafe...
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chafe v. 1 rub, warm (up), heat (up): I took the chill off my hands
by chafing them a bit. 2 rub, abrade, fret, gall, irritate,
make sore: The skin is very tender where it was chafed. 3
fume, rage, seethe; ruffle, vex, fret, irritate: I chafed in
impotent rage and exasperation at the ridiculous regulations.
To chafe and vex me is a part of her nature.
--n. 4 sore, abrasion, bruise, soreness, irritation: The
saddle caused a chafe on the inside of my thigh.
chaff n. 1 banter, raillery, ridicule, badinage, joking, teasing,
twitting, Colloq kidding, ragging, Chiefly US and Canadian
joshing: After the speech, he had to put up with a lot of
good-natured chaff from the audience.
--v. 2 banter, tease, twit, rail at, Colloq kid, rag, Chiefly
US and Canadian josh: When he was in the navy, his family
chaffed him for having a girl in every port.
chain n. 1 string, series, combination; sequence, succession, train,
course, set, concatenation: He owns a chain of bookshops.
Interruption of the food chain can cause serious ecological
consequences. A curious chain of circumstances led me to a small
hotel at Torquay in February. 2 restraint, check, trammel,
control, confinement, fetter, bond, manacle, shackle, gyve: The
family finally threw off the chains of poverty.
--v. 3 shackle, secure, fasten, bind, gyve; confine, fetter,
restrain, confine, restrict, tie, limit: Prometheus was chained