An abbreviation is a shortened form of a word or term. The shortened form may include letters, numbers, and symbols.

Abbreviation Full Term
CFM contamination free manufacturing
COO cost of ownership
CM3 cubic centimeter
RIE reactive ion etch

An acronym is an abbreviation that can be pronounced and used as a name.


Use the following guidelines for all forms of abbreviation.

When to Use In Text

Define any abbreviation/acronym you use unless its meaning is clearly understood by everyone in your audience. For example, the following are some abbreviations and acronyms that are generally understood by a technical audience.


Define an abbreviation/acronym at its first use in text unless the first reference is in a heading. In this case, either use the abbreviation/acronym or the full term in the heading, but define the abbreviation/acronym in the following paragraph.

In documents that have a lot of abbreviations/acronyms, include a list defining them. Even if using a list, you still must define them within the body of the document.

When defining an abbreviation, spell out the term and follow with the abbreviation in parentheses.

...documents the alpha site developmental activity for the Automatic Defect Classification (ADC) program. Several key steps, necessary to provide production-worthy ADC capability...

Unless the abbreviation is more familiar to your reader than its fully expanded term (for example, ASCII or NASA), do not abbreviate a phrase that appears only once or infrequently. The following term should not have been abbreviated because it is not used again and is not a familiar abbreviation.

...described model management and reusability, describing the Hierarchical Intelligent Simulation Environment (HISE) and how it could be used to facilitate...

When to Use In Graphics

Abbreviate in figures and tables to conserve space. Define possibly unfamiliar or ambiguous abbreviations in a note or key - even if they have already been defined in text - since a graphic may be read independently.


Use the definition of an abbreviation/acronym as it appears in the SEMATECH Technology Transfer Acronym and Abbreviation List. For additional sources, see REFERENCE WORKS.

How to Use

Articles Preceding Acronyms

The choice of a or an before an abbreviation/acronym depends on the way the abbreviation is pronounced. If the abbreviation begins with a consonant sound (including a sounded h or long u), use a. If it begins with a vowel sound, use an.

an ECR
a CIM system
an X-ray
a UHF channel
an RIE


Although the abbreviation or acronym may be all capitalized, the term it stands for often is not. Capitalize only proper nouns when defining an abbreviation/acronym.

Resource Conservation and Recovery Act (RCRA)
secondary ion mass spectroscopy (SIMS)
gallium arsenide (GaAs)

In an abbreviation of a term that includes proper nouns with prepositions, do not use lower case for the prepositions.

Cost of Ownership (COO) model
Department of Defense (DOD) contract

Chemical Abbreviations

Use formulas freely in tables and graphics. In text, spell out the name at its first reference, followed by the formula in parentheses. The formula alone may be used subsequently.

hydrofluoric acid (HF)
boron trichloride (BCl3)

To avoid ambiguity, it is preferable to spell out the word tungsten. However, if the word is used heavily within the same document, use of the symbol W saves time and space, and alleviates repetition.

Isotopes may be written as carbon-14 or 14C.

When written out, names of chemical elements and compounds are written in lowercase letters. The chemical symbols are capitalized as they appear in the periodic table of elements.

Measurements and Symbols


Plural Forms

Many abbreviations use the same form whether plural or singular.


Use 's only for abbreviations that end with periods or lowercase letters used as nouns.

x's and y's


Most abbreviations do not end with a period. Exceptions include abbreviations that may be confused with a word, are personal titles, or traditionally end with periods. Check punctuation in a standard REFERENCE WORK.


When an abbreviation that normally ends with a period appears at the end of a sentence, do not add a second period. the U.S. Further analyses indicate...

Set off i.e., e.g., and etc., as you would the full phrases they abbreviate. Both i.e. and e.g. should be immediately followed by commas. The type of punctuation that precedes them depends on sentence structure and context.

...on a cost-plus basis with no ceiling; i.e., there was no contractual limit on costs.

...aggressive lithography development in Japan, e.g., in phase-shift mask, cell projection E-beam direct wafer write, and X-ray lithography.

...level of automation, wafer size, and fab design capacity (i.e., wafer starts per day).

Always precede etc. with a comma. When it appears in the middle of a sentence, follow etc. with a comma as well.

A last-minute check should confirm that all references to other sections, figures, etc., remain correct.

State Names

Spell out the state name when used alone. When used with a city name, use the two-letter postal abbreviation.

Three universities in Texas participate...
...workshop held in Austin, TX, October 19-20.