He began his career helping his father, Clarence Barnhart, edit the Thorndike-Barnhart dictionary series.
In the 1980s Lexik House published ТРОйКА--The TROIKA Introduction to Russian Letters and sounds (c. 1980) by Reason A. Goodwin, the Dictionary of Bahamian English (c. 1982) by John A. Holm with Alison Watt Shilling, and in 1987 The Dictionary of Gambling and Gaming by Thomas L. Clark.
In 1982 he, with his father, began work on The Barnhart Dictionary Companion, a quarterly publication documenting appearance of new words, new meanings and new usages in English.
[5] He has worked as a teacher, lecturer, and as an expert witness reporting on usage and meaning in English words.
He is a member and past president of the Dictionary Society of North America and the International Linguistic Association.