Why Learn About Latin Words and Expressions in English?:
- You're studying for a vocabulary/admissions test.
- You're a non-native English speaker puzzled by the vocabulary.
- You're developing a character for a novel.
- You need a new word for a specific technical purpose.
- You are a stickler for language purity and don't want to create a hybrid word inadvertently. [See this "polyamory" t-shirt for more information.]
The Latin Connection With English:
It's confusing to hear that English doesn't come from Latin because there are so many Latin words and expressions in English, but vocabulary is not enough to make one language the daughter language of another. Romance languages, including French, Italian, and Spanish, come from Latin, an important sub-branch of the Italic branch of the Indo-European tree. The Romance languages are sometimes called daughter languages of Latin. English is a Germanic language, not a Romance or Italic language. The Germanic languages are on a different branch from the Italic.
Just because our English language doesn't come from Latin doesn't mean all our words have a Germanic origin. Clearly, some words and expressions are Latin, like ad hoc. Others, e.g., habitat, circulate so freely that we're not aware they're Latin. Some came into English when Francophone Normans invaded Britain in 1066. Others, borrowed from Latin, have been modified.
Latin Words in English:
There are many Latin words in English. Some are more obvious than others because they are italicized. Others are used with nothing to set them apart as imported from Latin. You may not even be aware they're Latin, like "veto" or "etc."
Latin Words Incorporated in English Words:
In addition to what we call borrowing (although there is no plan to return the borrowed words), Latin is used to form English words. Often English words contain a Latin word as a prefix. These Latin words are most often Latin prepositions. Many Latin words come into English with the preposition already attached to the verb. Sometimes the ending is changed to suit the needs of English; for instance, the verb may be converted to a noun.
Latin Sayings in English:
Some of these sayings are familiar in translation; others in their original Latin (or Greek). Most of them are profound and worth remembering (in either the classical or modern language).
More - Words and Ideas:
Words and Ideas, edited by William J. Dominik, contains word-building techniques for those who want to learn how to combine bits of Latin or Greek to form proper words in English or for those interested in the meaning of those word components.