Dictionary:Conventions Used

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As in the previous editions, I use the following conventions:

(1) Entries usually begin with the heart of a definition, although occasionally a discussion is given first to provide a frame of reference. Restrictions on meaning sometimes are contained in a discussion which follows rather than being incorporated into the definition itself. Terms indicated as being synonymous are often used interchangeably even though they may not be identical in all respects.

(2) The numbering within an entry indicates different meanings, but the sequence does not indicate preference. Where meanings are contradictory, this is stated explicitly and, in some cases, a preferred usage is indicated and an alternative suggested to avoid ambiguity. Letters subdivide an entry without implying differences in meaning. Only specialized meaning in geophysics are included.

(3) Words in italics refer the reader to another entry that supplements the meaning. Cross-references are shown only where needed to complete the meaning. They are indicated by “see,” “compare,” or “q.v.” (quo vide). Cross-references also indicate preferences. For example, “P-wave” is preferred to other terms meaning the same thing, so the other terms are referred to the P-wave entry. Likewise, “common midpoint” is preferred to “common depth point” or “common reflection point” because it expresses more accurately what it is that is common.

(4) Bold face within an entry indicates additional terms that are (in effect) defined here.

(5) Tradenames are indicated where they are in general use. Where used for a class of devices, an entry may begin with a lower-case letter even though the tradename begins with a capital. Neither inclusion nor exclusion of tradenames implies judgments about the merits of devices or processes.

(6) References suggest a place to begin looking for further information. Readers who want more information will generally find additional sources suggested in the cited references. References are listed in the back. Usually a readily available single source is cited. The citation of a reference does not imply the original source nor the most complete or current reference.

(7) Figures have been kept simple to illustrate the terminology and the most important features of concepts without attempting to make them realistic or illustrate all features. Figures, tables, and boxes have been incorporated into one sequence identified numerically within each letter of the alphabet to aid in locating them. Entries that are most apt to be used for reference are listed immediately following the table of contents.

(8) Pronunciations are indicated by the fairly simple code listed in the separate Guide to Pronunciation. I found appreciable differences in pronunciation (as well as in definitions) among the dictionaries I consulted (Guralnik, 1972[1]; Jackson, 1997[2]; Morris, 1969[3]; Oxford, 1971[4]; Parker, 1989[5]; Stein, 1966[6]), some making subtle distinctions that seem unnecessary.

(9) I have attempted to conform with current SEG practice as to whether compound words are one word, hyphenated, two words, or italicized. Such decisions are sometimes arbitrary.


  1. Guralnik, D., 1972, Webster's New World Dictionary.
  2. Jackson, J. A., 1997, Glossary of Geology, 4th Ed.: Alexandria, VA, American Geologic Institute.
  3. Morris, W., Ed., 1969, American heritage dictionary of the English language: Houghton Mifflin Co.
  4. Oxford, 1971, Oxford English dictionary: Oxford Univ. Press.
  5. Parker, S. P., Ed. 1989, McGraw-Hill dictionary of scientific and technical terms, 4th Ed.: McGraw-Hill Book Co.
  6. Stein, J., Ed., 1966, Random House dictionary of the English language: Random House, Inc.