(sic): You write (sic) in brackets after a word or expression when you are quoting something that someone else has said or written.
Example: She said that she liked very much London (sic) and wanted to stay here for a long time.
A priori: Based on theory rather than observation
Example: The fact that their house is in such disrepair suggests a priori that they are having financial difficulties.
Ad absurdum: To the point of absurdity
Example: He tediously repeated his argument ad absurdum.
Ad hoc: As an adjective, it means "formed or created with a specific purpose," and as an adverb, it means "for the specific purpose or situation."
Examples: i) The World Bank's board on Friday ordered an ad hoc group to discuss the matter.
ii) The ad hoc committee disbanded after making its final report.
Ad infinitum: To infinity
Example: The lecture seemed to drone on ad infinitum.
Ad Nauseam: If something that happens over and over again so that people get completely bored
Example: He talked ad nauseam about his achievements and how successful he is. It was boring!
Addendum: An item to be added, especially a supplement to a book. The plural is addenda.
Example: I will sign the contract once an addendum is included to require the lessor to repaint the apartment within 60 days.
Alma Mater: One's old school
Example: Central High School is my alma mater.
Alter ego: Other (alternative) self
Example: A person with an alter ego is said to lead a double life
Annus mirabilis: Wonderful year
Example: Last year was the annus mirabilis for my company.
Example: Aqua aerobics is a water workout that improves fitness whilst protecting the joints.
Bona fide: In good faith; genuine
Example: For all her reticence and modesty, it was clear that she was a bona fide expert in her field.
Carpe diem: Seize the day
Example: So what if you have an 8:00 a.m. meeting tomorrow and various appointments? Carpe diem!
Casus belli: An act justifying war
Example: The general felt that the banana republic's insolent remarks about our national honor were enough of a casus belli to launch an attack.
Caveat emptor: Let the buyer beware
Example: Before you leap at that real estate deal, caveat emptor!
Census: Count of citizens
Example: Census of the population is being taken for the purpose of assessing revenue.
Example: The figure is wearing a heavy collum around the front of the neck, with a wide pendant in the center.
Example: As an optimist, he believes the show will start again cras even after several failures.
De Facto: "Actual" (if used as an adjective) or "in practice" (if used as an adverb).
In legal terms, de facto is commonly used in contrast to de jure, which means "by law." Something, therefore, can emerge either de facto (by practice) or de jure (by law).
Examples: i) Mama was in bed all day every day, suffering from depression; my sister was my de facto mother.
ii) Although his title was prime minister, he was de facto president of the country.
iii) In this prominent position, she's making her own de facto debut as a writer with a message for the general public.
Dei Gratia: By the grace of God
Example: De Gratia, he survived a very bad road accident last week and is safe and healthy now.
Deus ex machine: A contrived device to resolve a situation
Example: Stretching plausibility, the movie concluded with a deus ex machina ending in which everyone was rescued at the last minute.
E.g. (exempli gratia): For Example
Example: I buy many things in this shop e.g. video game player
Erratum: Error; mistake
Example: Lists of errors from a previous publication are often marked "errata" (the plural, meaning errors).
Et cetera: And the rest
Example: We urgently need to buy medical equipment, drugs et cetera.
Ex cathedra: With authority; used especially of those pronouncements of the pope that are considered infallible.
Example: I resigned myself to obeying; my father's opinions were ex cathedra in our household.