infectious

infectious — adjective

1. describes a sickness that can travel from one living thing to another through th

1.形容詞B1
釋義

describes a sickness that can travel from one living thing to another through the air, water, or touch

例句

The flu is highly infectious and spread through the school within a week.

collocation: highly infectious

Doctors warned that the virus remained infectious on metal surfaces for up to three days.

remain + infectious (linking verb pattern)

同義詞
  • contagious

    more specific — describes diseases spread through direct touch or contact, not air or water

  • communicable

    more formal — used in official health notices and medical writing

  • transmissible

    technical — used for diseases that can be passed between organisms, often through blood or fluids

反義詞
  • non-infectious

    describes a disease that cannot spread to others

  • non-communicable

    formal term for diseases like diabetes or heart disease that cannot be passed between people

文法句型

infectious + noun (disease, illness, virus)

be / remain / become infectious

用法筆記

Commonly placed before a noun to name the disease type (infectious disease, infectious virus). Distinguish from contagious: contagious describes diseases passed specifically through touch or close contact, while infectious can also include airborne or waterborne spread.

常見錯誤

❌I caught an infectious cold from shaking hands with my colleague.
✅I caught a contagious cold from shaking hands with my colleague.
💡Colds spread through touch, so contagious is more precise for contact-based transmission.
❌The doctor said my wound was infectious.
✅The doctor said my wound was infected.
💡A wound that has the disease inside it is infected; infectious means it can spread to others.

2. describes a person or animal who has a sickness that could spread to other peopl

2.形容詞B1
釋義

describes a person or animal who has a sickness that could spread to other people, animals, or plants around them

例句

Tara was still infectious after her fever faded, so she kept wearing a mask.

be + still/no longer + infectious (state of person)

The vet said the puppy was infectious and needed to stay away from other dogs.

同義詞
  • contagious

    same meaning for people carrying a disease, but slightly more common in everyday speech

  • infected

    focuses on having the disease inside the body, not necessarily on the ability to spread it

  • carrying

    informal — 'carrying a virus' suggests the person may not show symptoms

反義詞
  • immune

    protected against a disease and unable to catch or spread it

  • recovered

    no longer has the disease and therefore cannot spread it

文法句型

be infectious

remain infectious

become infectious

no longer infectious

用法筆記

Almost always used after a linking verb (be, remain, become, feel) rather than before a noun. Unlike sense 1, you would not say 'an infectious person' to mean a person carrying disease — instead say 'a person who is infectious' or 'an infected person.'

常見錯誤

❌The doctor said I am an infectious patient.
✅The doctor said I am still infectious.
💡For people, infectious follows a linking verb; placing it before a noun sounds unnatural in medical contexts.

3. describes an emotion, quality, or activity that quickly spreads among a group of

3.形容詞B2
釋義

describes an emotion, quality, or activity that quickly spreads among a group of people and makes them feel the same way or want to take part

例句

Manuela's infectious laughter filled the room and soon everyone was smiling.

infectious + laughter (most common figurative collocation)

The coach's infectious enthusiasm made the whole team train harder than ever.

同義詞
  • contagious

    works figuratively too (contagious laughter), but sounds slightly more playful or less formal

  • catching

    informal — 'His good mood was catching' is friendly and natural in speech

  • compelling

    stronger — suggests a force that makes people feel they must follow or agree

反義詞
  • dull

    describes a mood or atmosphere that does not excite or spread

  • unexciting

    describes something that fails to spark interest in others

文法句型

infectious + noun (laughter, enthusiasm, joy, energy, excitement)

be infectious

用法筆記

This is the figurative (metaphorical) sense — feelings, not germs, are doing the spreading. Most common with nouns for positive emotions: laughter, enthusiasm, joy, excitement, energy. Cannot be used for negative emotions (sadness, anger) — those are described as contagious in informal use, but not infectious.

常見錯誤

❌Her sadness was infectious and made everyone cry.
✅Her sadness spread through the room and made everyone cry.
💡Infectious is rarely used for negative emotions in standard English.