series and lists (APA 6th, 3.04; CMS 17th, 6.127–6.132)
- Parallelism: Items in series should be parallel in form (e.g., a series of nouns and noun phrases, of verbs and verb phrases, of gerunds, of infinitives, of dependent clauses, or of sentences [see parallelism]).
- Run-ins and vertical lists: A series may occur within a paragraph or sentence (called a run-in list), or as separate items listed independently at or near the left margin (called a vertical list or outline style). According to CMS 17th, 6.128, short, simple lists are better run in than set in a vertical list. See examples in CMS 17th, 6.129.
- Enumeration: Use a logical and consistent system of letters, numerals, or bullets for identifying items in series:
- According to APA 6th, 3.04, enumerated elements in a run-in list are normally identified by lowercase roman letters enclosed in parentheses. For example,
A perfect vacation requires careful timing: (a) a week to unwind from the stresses of the office; (b) a week of all-out, vigorous exercise; (c) a week of exploration, discovery, and creative play; and (d) 49 weeks to plan the next vacation.
- If the introductory phrase or clause refers to a specific number of items in the series, or if the sequence of items is significant (highest to lowest, first to last, or similar arrangement), the elements are identified by arabic numerals.
In run-in style, items in a numbered list are identified by arabic numerals enclosed within parentheses. Note the punctuation in the following example:
The secret of guilt-free parenthood may be found in these four rules: (1) never make a rule you might someday have to change, (2) never make a promise you might someday have to break, (3) never take a chance you might someday regret, and (4) never have children, period. [Note the rhetorical effect of item 4, which would be lost if that item were placed anywhere else in the sequence.]
In a vertical list of numbered items, use arabic numerals, each followed by a period (e.g., 1.).
- A vertical list whose items need not be enumerated (e.g., the items could just as easily appear in a different sequence) should be bulleted, as follows:
Your home is probably full of objects with bright, colorful print that your child can recognize as meaningful:
- Cereal boxes and other food containers
- Laundry and household products
- Magazine covers and advertisements
- The child's name on clothing, pillows, cubby, toy box, and lunch pail
- Punctuate items in a vertical list as follows (see CMS 17th, 6.124–130):
- If items in the list are sentences, begin each one with a capital letter and end each one with a period (CMS 17th, 6.130).
- If listed items are longer phrases or clauses, begin each item with a capital letter and use no punctuation at line-ends (CMS 17th, 6.130).