Sludge

How to spell sludge

6 letters · 1 syllable

How to pronounce sludge

What does sludge mean?

1. nounThick, soft, muddy material, especially the semi-solid residue produced by sewage treatment, oil refining, or industrial processes.

Sludge in a sentence

• The treatment plant separates clean water from the heavy sludge at the bottom of the tank.

• Engineers found a layer of black sludge clogging the bottom of the old fuel tank.

Where does sludge come from?

Language of origin: Unknown

Sludge first appears in English in the early 1600s, and its exact origin is genuinely uncertain. It looks to be an imitative or expressive word, coined to capture the squelching, oozing feel of thick wet mud, and it sits in a small family of similar-sounding words including 'slush', 'slutch' (a dialect word for mire), and 'slosh'. Some scholars treat it as a direct variant of 'slutch', with the soft -dge ending substituted for the -tch. The early meaning was simply soft, semi-liquid mud or mire; only later, with industry and sewage treatment, did it take on the technical sense of the muddy residue left after settling or filtering. Because the word is essentially sound-symbolic rather than borrowed from a classical root, the spelling is a trap: the -dge captures the same soft 'j' sound you hear in 'bridge' and 'judge'.

How the word is built

• sludge (single root, no prefix or suffix; an imitative word formed as a blend-like variant of 'slush' and 'slutch')