Longest Word in the English Language Dictionary

At 45 letters Pneumonoultramicroscopicsilicovolcanoconiosis is the longest non-scientific/place-name word in any English language dictionary.

The word appears in the 1936 Supplement to OED1, the OED2, the addendum to W2 (spelled -koniosis), W3 (spelled -coniosis), RHUD2, and Chambers.

The OED2 has:

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