final: Sometimes misused in such a sentence as "the final completion of the work." This is inadmissible, for completion necessarily implies finality.
financial, monetary, pecuniary: Discriminate carefully between these words. Financial is applied correctly to public funds or to the revenue of a government. Monetary and pecuniary apply only to transactions between individuals.
finish. Compare complete.
fire: As this verb possesses the sense of impel, explode, discharge, as by using fire; as, "fire a mine or gun," it has been humorously applied to discharge from employment, as "fire a clerk." But the usage is slang, and as such is avoided by careful speakers.
first: Say the "first two" rather than the "two first," for unless they be bracketed equal there can not be two firsts. For a similar reason the expression seen in cars, "Smoking on the four rear seats," is equally incorrect. There can not be four rear (or last) seats; but there can be "the last four seats." As meaning the four seats collectively which are situated at the rear, the phrase has its only justification.
first and firstly: First being an adverbial form is the correct form to use. Firstly has been used by Dickens, De Quincey, and others but in modern usage first is the preferred form.