De elegantiis terminorum

Faustum prosperous/lucky comes from favendo favoring. Infaustum unlucky is the opposite, meaning infortunatum unfortunate.

Faber artisan/craftsman is not said only of those working in metal, as the common people believe, nor only of those working in wood, but of all those who use a hammer for construction. Therefore, when making an addition, one must say faber lignarius carpenter or faber argentarius silversmith.

Facies face is what one has from nature, and it refers to the appearance of the whole body. Thus, we have superficies surface. But vultus countenance comes from voluntate will/intent and refers to that.

Faciliter is barbaric; the Latin is simply facile easily.

Facinus deed/crime is something done; it is taken in a bad sense, or in a good sense, according to the adjective attached to it.

Factio faction is a consensus or conspiracy of wicked people, or a division of citizens. Hence factiosi factious people are those who create such a division by right or wrong. Seditio sedition is when matters come to blows, when there is discord with the people themselves, spoken of separately.

Fateri to confess/admit is to do so under compulsion; profiteri to profess/declare openly is to do so voluntarily. Hence professor and professio.

Flagrans burning, through an 'l', signifies burning with fire, by breath, or flame. But fragrans fragrant, through an 'r', signifies an odor.

Fenero tibi means I give money to you at interest.
Feneror abs te means I receive money from you at interest.

We say fero and perfero to bring/carry letters; we do not use affero for this.

Festus festive pertains to a feast, as in dies festus a feast day. But festivus pertains to other matters, as in festiva oratio a pleasant or witty speech; festivum caput a witty person.

Flere to weep is with tears. Gemere to groan is to feel pain in the chest. Plorare to cry out is to manifest one's pain with a mournful and flowing voice. Plangere to lament is to afflict oneself with the striking of limbs or pain. Eiulare to wail is to weep with a loud voice, which is more womanly. Vociferari to shout is to show not only pain but also indignation with an unbridled voice. Lamentari to lament is to testify to one's misfortune with a querulous voice and sad speech. Luctus grief is the pain which is signified externally by the face and appearance; sometimes it is taken for mourning attire.

Frequens locus is a place where many live, such as a town, or where many dwell, such as a marketplace or a plaza. It is also said of living things, as "the soldier is frequens" (meaning numerous and assiduous); "the crowd is frequens"; "the students are frequentes".

Fretus sum means "I am trusting," not "I am among islands."

Fio has compounds like calefio or frigefio, but these are not used by the learned; instead, they use calesco or frigesco. However, many are in use, such as madefio and patefio. Those ending in '-sco' signify a passion caused internally; those in '-fio' signify a passion inflicted externally. For example, calesco is from within; calefio is from without.

Faciendus is correct, not ficiendus.