A Guide to In-Line Lists

By Mark Nichol

This post describes how to organize in-line lists, those that occur within a sentence, as compared to vertical lists, those organized by setting the items on the list apart from each other, distinguished by numbers, letters, or other symbols, on consecutive lines. (Vertical lists will be described in a separate post.)

An in-line list may consist of a set of words, phrases, or clauses, or a combination of the three. The simplest in-line list is one that consists of one-word items: “The colors of the American flag are red, white, and blue.” (Style guides differ on whether the comma preceding and, called a serial comma—or, sometimes, an Oxford comma—is necessary, but consistent use helps writers avoid creating ambiguously organized sentences.)

More complex lists invite errors. For example, in the following sentence, the syntax of the list items is not consistent:

“Children raised in a traditional two-parent household tend to be physically and emotionally healthier, less likely to use drugs and alcohol, engage in crime, or become pregnant outside of marriage.”

One can analyze the sentence by converting it into an introductory phrase followed by a vertical list. Note how the items are not parallel in structure:

Children raised in a traditional two-parent household tend to be

  • physically and emotionally healthier
  • less likely to use drugs and alcohol
  • engage in crime
  • become pregnant outside of marriage.

A technically correct revision follows:

Children raised in a traditional two-parent household tend to be

  • physically and emotionally healthier
  • less likely to use drugs and alcohol
  • less likely to engage in crime
  • less likely to become pregnant outside of marriage.

However, the repetition of the phrase “less likely to” is distracting and is redundant to “tend to be,” and further revision of this vertical list is recommended if it is to be converted back to an in-line list.

Because the four elements in this sentence are not consistently supported by verbs or verb phrases, it is best to separate the first item from the rest of the items, resulting in a sentence consisting of two elements that include examples—the first example standing on its own, and the other three retained as a three-item list:

“Children raised in a traditional two-parent household tend to be physically and emotionally healthier and are less likely to use drugs and alcohol, engage in crime, or become pregnant outside of marriage.”

If one or more elements in an in-line list include a comma, a stronger punctuation mark, the semicolon, must be employed to clarify the organization of the sentence. This is true when at least one element includes a single comma that sets off, for example, the name of a city and the name of a state, as in this example:

“Unusual names of cities and towns include Cut and Shoot, Texas; Truth or Consequences, New Mexico; and Rough and Ready, California.”

Semicolons are also called for when one or more items in an in-line list are themselves lists, as shown here:

“Unusual names of cities and towns include Cut and Shoot, Truth or Consequences, and Rough and Ready; Embarrass, Uncertain, and Waterproof; and Accident, Hazard, and Protection.”

Note that although some writers use semicolons to separate items in a list when the items are long and complex, doing so is unnecessary. Thus, the intervening punctuation marks in the following example are safely converted to commas: “Uncertainties include the volatility in oil and gas prices; concerns about the impact of economic sanctions in Russia to U.S. and European markets; questions about slowdowns in China; and the effects on U.S. economic policy resulting from the shift in power in the U.S. Senate in January 2015.”

This is especially true if an additional clause follows the last list item, creating the implication that the clause applies only to the final item. Here, it is necessary to convert the semicolons after function and shareholders to commas: “If the chief executive officer is not willing to pay attention to the warning signs posted by the risk management function; the reward system is not sufficiently balanced with the long-term interests of shareholders; or the board is not asking tough questions about the assumptions and risks underlying the strategy, it is not likely risk management will have an impact at the crucial moment when a contrarian voice is needed.” Otherwise, the phrase beginning “it is not likely risk management . . .” would have appeared (at least when first read) to pertain only to the phrase beginning “the board is not asking tough questions . . . .”

Also, semicolons are not necessary when separating only two sets of list items, rather than three or more. In the following example, or is sufficient to distinguish the two lists, and the semicolon should be omitted: “This strategy may span several departments—for example, legal, procurement, and finance; or marketing, sales, and customer service.”

Also, to aid in distinguishing items in a list, the items are sometimes preceded by sequential numbers (or, occasionally, lowercase letters) followed by a close parenthesis rather than a period, as in this example: “The three forms of rock are 1) igneous, 2) metamorphic, and 3) sedimentary.” This method of organization can be useful for enumerating and setting off complex list items (or, in the case of letters, offering options), but it is usually unnecessary, or a vertical list (without numbers or letters) may be a better option.


Leave a comment: