parasite

parasite — noun

1. a small living thing such as a worm, insect, or tiny organism that survives by f

1.nounB2
Definition

a small living thing such as a worm, insect, or tiny organism that survives by feeding off the body of a larger animal or plant, which is called its host.

Example

Mosquitoes can carry a parasite that causes malaria in humans.

parasite + that-clause naming the disease

The vet checked the dog's fur for fleas, ticks, and other parasites.

listing common examples of parasites

Common collocations
  • intestinal parasite
  • blood parasite
  • kill parasites
  • carry a parasite
  • parasite infection
Synonyms
  • bloodsucker

    informal; usually for parasites that drink blood, like leeches or ticks.

  • pest

    broader term for any harmful insect or small animal, including ones that aren't parasites.

Antonyms
  • host

    the animal or plant that the parasite lives on or in.

Grammar Patterns

parasite + of/in/on + host noun

Usage Note

Often used in the pattern 'a parasite of/in/on [host]'. Frequently appears with words like host, infect, infection, and disease, which together signal the biology sense.

Common Mistakes

A virus is a parasite of the lungs.
A flu virus infects the lungs.
in everyday English, 'parasite' usually means a worm or small animal; viruses and bacteria are normally called germs, viruses, or bacteria, not parasites.
The dog has a parasite in his ear.' (when meaning earwax or dirt)
The dog has wax in his ear.
'parasite' must be a living thing that feeds off the host.

2. an insulting word for someone who keeps living off the money, work, or kindness

2.nounC1
Definition

an insulting word for someone who keeps living off the money, work, or kindness of others while giving very little back in return.

Example

The newspaper called the lazy heir a parasite on his hardworking family.

pattern: a parasite on + group

Marcus felt like a parasite after living rent-free at Sara's flat for a year.

self-description: feel like a parasite

Common collocations
  • a parasite on society
  • social parasite
  • lazy parasite
  • feel like a parasite
Synonyms
  • leech

    very similar in tone; suggests draining money or energy from one specific person.

  • freeloader

    milder; someone who takes free meals, rides, or rooms without paying.

  • sponger

    British informal; someone who keeps borrowing money or living off others.

Antonyms
  • contributor

    someone who actively gives time, money, or effort to a group.

  • breadwinner

    the family member who earns the income that supports others.

Grammar Patterns

a parasite on + group/society

Usage Note

Strong negative term — close to 'leech' or 'sponger'. Distinguish from sense 1 by context: when the noun refers to a person and there is no biological host, you are in this sense. Avoid using it about real people in formal writing; it sounds harsh and judging.

Common Mistakes

My little brother is such a parasite when he asks me for snacks.
My little brother is so annoying when he asks me for snacks.
'parasite' is too strong for everyday family teasing; save it for serious criticism.
She is a parasite to her parents.
She is a parasite on her parents.
the typical preposition is 'on', not 'to'.

Word family

  • parasitic
    adjectiveC1
  • parasitical
    adjectiveC2
  • parasitism
    nounC2
  • parasitology
    nounC2
  • parasitologist
    nounC2

Synonym discussion

Sense: noun/2

All four words describe someone who lives off others, but they differ in tone and target. 'Parasite' is the harshest and most moral, often used in serious writing about whole groups, as in 'parasites on society'. 'Leech' is also strong but feels more personal — it suggests one person draining another's money or emotional energy, as in 'her ex-boyfriend was a real leech'. 'Freeloader' is the mildest and most everyday: someone who shows up for free food, free rides, or a free couch without offering anything back. 'Sponger' is mainly British and informal, often used for someone who keeps borrowing small amounts of money. Choose 'parasite' or 'leech' for sharp criticism; pick 'freeloader' for casual complaints among friends.

parasite ↗leechfreeloadersponger

Common collocations

Nouns

  • parasite infection
  • parasite control
  • host of a parasite
  • blood parasite
  • intestinal parasite

Phrases

  • carry a parasite
  • kill parasites
  • treat for parasites
  • infected with parasites

Prepositions

  • a parasite on (society/the system)
  • a parasite of (a host species)
  • a parasite in (the gut/blood)

Etymology

GreekLatinFrenchEnglish

Came into English in the mid-1500s from Latin 'parasitus' and earlier Greek 'parasitos', which literally meant 'someone who eats beside another' — formed from 'para-' (beside) and 'sitos' (food, grain). In ancient Greek comedy, a parasitos was a stock character who flattered rich hosts in exchange for free meals, so the human, freeloader meaning is actually older in English than the biology meaning, which scientists adopted in the 1600s and 1700s when they noticed organisms that feed off larger animals and plants.