shellfish

shellfish — noun

1. a group of sea animals that have a hard shell covering their body, many of which

1.nounB1
Definition

a group of sea animals that have a hard shell covering their body, many of which people eat as food — for example, crabs, oysters, shrimp, clams, mussels, and lobsters

Example

The restaurant menu offers a variety of fresh shellfish, including clams and mussels.

uncountable: shellfish as a food category

Noa checks each shellfish carefully before cooking them, throwing away any that are open.

countable plural: each individual shellfish

Common collocations
  • fresh shellfish
  • raw shellfish
  • cooked shellfish
  • shellfish allergy
  • shellfish poisoning
  • gather shellfish
  • harvest shellfish
Synonyms
  • seafood

    broader term that includes fish, shellfish, and other edible sea creatures

  • molluscs

    narrower term that excludes crustaceans (crabs, shrimp, lobsters)

  • crustaceans

    narrower term that excludes molluscs (clams, oysters, mussels)

Usage Note

Countable when referring to individual animals ('a shellfish', 'three shellfish on the beach'); uncountable when referring to the food as a category ('shellfish is a common cause of food allergies'). The word covers two biologically distinct groups — molluscs (clams, oysters, mussels) and crustaceans (crabs, shrimp, lobsters) — which are grouped together for culinary and dietary purposes.

Common Mistakes

I ate shellfishs for dinner last night.
I ate shellfish for dinner last night.
Shellfish has the same form in both singular and plural, like 'fish' or 'deer.'
Shellfish are a type of fish.
Shellfish are not fish
they are invertebrates with hard shells.' — Despite the name, shellfish belong to different animal groups than fish.

Word family

  • shell
    nounA2
  • shelled
    adjectiveB2
  • shelly
    adjectiveC1
  • shell-less
    adjectiveC2

Synonym discussion

Sense: noun/1

Seafood is the broadest of these terms, covering all edible creatures from the sea — fish, shellfish, seaweed, and marine mammals. Shellfish narrows the focus to invertebrate animals with a hard outer shell, a category that spans two biologically distinct groups: molluscs (clams, oysters, mussels, scallops) and crustaceans (crabs, lobsters, shrimp, prawns). While molluscs have soft, unsegmented bodies protected by a calcium-carbonate shell, crustaceans have jointed legs and a segmented exoskeleton. Despite these biological differences, English groups them together as 'shellfish' because they share a shell-like exterior and are often prepared and eaten in similar ways. In everyday conversation people use 'shellfish' when ordering food, discussing allergies, or buying from a seafood market — for example, 'I will have the shellfish platter, please' or 'Does this sauce contain any shellfish?'

seafood ↗molluscscrustaceans

Common collocations

Nouns

  • shellfish farmer
  • shellfish bed
  • shellfish industry
  • shellfish poisoning

Phrases

  • shellfish on the half shell
  • shellfish platter

Prepositions

  • allergic to shellfish
  • shellfish from the bay

Etymology

Old EnglishMiddle EnglishEnglish

Shellfish comes from Old English 'scell' (meaning a hard outer covering) combined with 'fisc' (fish). Despite the name, shellfish are not actually fish — they belong to entirely different animal groups: molluscs and crustaceans. The word has been used since Old English times to describe any water-dwelling creature with a shell that people could collect and eat.