Irregular chess opening
infrequent and unorthodox chess opening
In chess, an irregular opening is an opening considered unusual or unorthodox. In the early 19th century the term was used for any opening not beginning with 1.e4 e5 (the Open Game) or 1.d4 d5 (the Closed Game). As opening theory has developed and openings formerly considered "irregular" have become standard, the term has been used less frequently.
Because these openings are not popular with chess players, the standard opening references such as Modern Chess Openings (MCO) and Encyclopaedia of Chess Openings (ECO) do not cover them in detail.
Usage of the term
While the term has frequently been used in chess literature, its meaning has never been precise and has varied between writers.
One of the earliest references to "irregular openings" in chess literature was made by William Lewis in his 1832 work Second Series of Lessons on the Game of Chess. Lewis classified openings under the headings "King's Bishop's Game" (1.e4 e5 2.Bc4), "King's Knight's Game" (1.e4 e5 2.Nf3), "Queen's Bishop's Pawn Game" (1.e4 e5 2.c3), "King's Gambit" (1.e4 e5 2.f4), "Queen's Gambit" (1.d4 d5 2.c4) and "Irregular Openings" (all other openings). Lewis comments that the irregular openings are "seldom played, because they are generally dull and uninteresting". Among the openings he analyzes under this heading are the French Defence and English Opening (both now considered standard), Bird's Opening and a few 1.d4 d5 lines without the Queen's Gambit. Lewis assigns no names to these openings.
Begin with the source’s own compact description: “Irregular chess opening” is infrequent and unorthodox chess opening. The dossier treats that line as a proposition to test through Irregular, chess and opening, not as a finished interpretation.
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