Comma titles that follow a name: "John Smith, Ph.D." Similarly in lists that are presented with an inversion: "...; socks, green: 3 pairs; socks, red: 2 pairs; tie, regimental: 1". Commas may be used to indicate that a word, or a group of words, has been omitted, as in "The cat was white; the dog, brown." (Here the comma replaces "was".) Commas are placed before, after, or around a noun or pronoun used independently in speaking to some person, place or thing: In his 1785 essay "An Essay on Punctuation", Joseph Robertson advocated a comma between the subject and predicate of
Punctuation of English in text messaging and other short-form online communication, where more formal or "closed" punctuation can be misinterpreted as aloofness or even hostility. Open punctuation eliminates the need for a period at the end of a stand-alone statement, in an abbreviation or acronym (including personal initials and post-nominal letters, and time-of-day abbreviations), as well as in components of postal addresses. This style also eschews optional commas in sentences, including the serial comma. Open punctuation also frequently drops apostrophes. Open punctuation is used primarily in certain forms of business writing, such as letterhead and envelope addressing, some business letters, and résumés and