Please, specify American/British Engilsh!
I think these below are very common but I have no idea if they are commonly used in spoken English.

ad hoc
per se
a priori
de facto
et cetera
vice versa

Edit: Which are the Latin words/phrases understood and used by everyone?


I searched the Corpus of Contemporary American English (COCA), limiting results to the spoken sub-corpus, which contains 95 million words of unscripted spoken English. I included whatever alternative spellings or misspellings I could think of; since my goal here was to find words as they were spoken, spelling was irrelevant.

Here's the raw data:

  et cetera         1529
  (etcetera)        208
  (etc)             813
  ad hoc            94
  a priori          3
  de facto          221
  (de facto)        3
  ergo              19
  vice versa        253
  (vise versa)      1
  per se            459
  (per say)         6

Combining the above and sorting in descending order, I get these results:

  et cetera         2550    (most common)
  per se            465
  vice versa        254
  de facto          224
  ad hoc            94
  ergo              19
  a priori          3       (least common)

These results may not reflect spoken American English in general. They don't represent British English, which may or may not be different.

These results correspond roughly with my intuition as a native speaker of American English, for what it's worth. All of these lexical items are used in spoken English, but not all are used with equal frequency.


ad hoc -- common among academic writers, widely known among educated people, but not common in casual speech

per se -- reasonably common among everyone educated, but not that common in casual speech.

a priori -- only in legal and academic writing.

de facto -- common among educated people, widely used in newspapers and journals, but not that common in speech.

ergo -- pretentious, not used, but widely understood. often used to make fun of people who are acting too sophisticated.

et cetera -- understood and used by everyone in all registers of language. sometimes colloquially pronounced "egg cetera" especially among less educated people.

vice versa -- understood and used by everyone. first syllable is pronounced to rhyme with "nice" as though it were a native English word. Sometimes colloquially prnounced "vice-a versa."

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