When does a word become part of English vocabulary? You could argue that the first time anyone invents a new word and uses it, it has become part of the vocabulary, because it exists, but if no one else knows about it, the word won’t exist for very long. New words that get picked up and used by more and more people are generally referred to as “slang” when they describe part of popular culture, and often reach that tipping point where they’re so much in use that they’re considered ordinary, and no longer slang. Some new words enter the vocabulary from specialized fields, such as medicine or physics, as new concepts and compounds are created that require new words to describe and define them, but these words often do not become part of ordinary spoken English.

For many people, a word is “officially” part of the English language when it is finally included in the Oxford English Dictionary. Since the 1800s the committee members at the OED have been evaluating and categorizing words, and are currently working on a Third Edition of the OED (the Second Edition was published in 1989). The print version of the OED is rather inconveniently large to carry around (20 volumes!) but you can subscribe to the on-line edition (go to www.oed.com) for a yearly fee. New words are added four times a year, as well as revisions to existing words and definitions.

The June 2010 additions include these entries:

caffè ristretto: The Italian (and now English) term for a “short shot” of espresso made with less water and/or finer coffee grounds, producing a more intense and concentrated liquid.

geoengineering: Manipulating aspects of Earth’s structure or climate to affect the planetary system on a global scale.

hindbrain: The lower rear portion of the brain that contains the segments responsible for automatic functions such as breathing.

hot-dogging: A term used in sports such as surfing, skiing, snowboarding, and skateboarding, this describes the act of performing showy or daring stunts and tricks.