bulb

bulb — noun

1. the small glass unit in an electric light that glows when power is on.

1.nounB1
Definition

the small glass unit in an electric light that glows when power is on.

Example

Diego changed the bathroom bulb before the guests arrived.

collocation: change a bulb

A dead bulb left the hall dark all night.

a bulb goes dead

Common collocations
  • change a bulb
  • replace a bulb
  • screw in a bulb
  • dead bulb
  • LED bulb
Synonyms
  • light bulb

    the full everyday phrase; clearer when context is missing

  • lamp

    often means the whole light fixture, not only the glass part

  • LED

    often refers to a modern bulb type or its lighting technology

Grammar Patterns

change a bulb

a bulb goes dead

screw in a bulb

Usage Note

Usually names the replaceable shining part, not the whole lamp or light fitting. Common verbs are change, replace, fit, and screw in.

Common Mistakes

The bulb on my desk is broken, so I need a new bulb and stand.
The lamp on my desk is broken, so I need a new lamp.
'bulb' is only the part that gives light; the whole object is usually a 'lamp'.
The lamp is dead, just buy a new lamp.
The bulb is dead, just buy a new bulb.
When only the shining part has failed, use 'bulb', not 'lamp'.

2. the thick round part under the ground that stores food and later sends up a new

2.nounB2
Definition

the thick round part under the ground that stores food and later sends up a new plant, as in tulips or onions.

Example

Priya planted tulip bulbs along the front path before winter came.

collocation: plant bulbs

Each bulb sent up green leaves after the first warm week.

intransitive growth: a bulb sent up leaves

Common collocations
  • plant bulbs
  • spring bulbs
  • flower bulbs
  • onion bulb
  • lily bulb
Synonyms
  • corm

    a similar plant part, but botanically different and less common in everyday speech

  • tuber

    another food-storing plant part, usually not layered like a bulb

  • root

    a broader everyday word; not every root is a bulb

Grammar Patterns

plant bulbs

a bulb grows

lift bulbs from the ground

Usage Note

Often used for garden plants that are planted one season and flower in the next. Distinguish from an ordinary root: a bulb is the round food-storing part that can grow a whole new plant.

Common Mistakes

The tulip root was dry, so we planted it in a pot.
The tulip bulb was dry, so we planted it in a pot.
Tulips grow from bulbs, not from ordinary roots.

3. the little glass section at the bottom of a thermometer that holds the liquid be

3.nounC1
Definition

the little glass section at the bottom of a thermometer that holds the liquid before it moves up the tube.

Example

The nurse shook the thermometer until the liquid fell back into the bulb.

thermometer liquid in the bulb

On the lab table, the bulb held red liquid below the scale.

bulb held liquid

Common collocations
  • thermometer bulb
  • liquid in the bulb
  • crack in the bulb
  • bulb at the bottom
Synonyms
  • bulb end

    a descriptive phrase rather than a fixed technical term

  • reservoir

    more technical; focuses on the part that holds the liquid

  • chamber

    a general word for an enclosed space, not specific to thermometers

Grammar Patterns

the bulb of a thermometer

liquid in the bulb

crack the bulb

Usage Note

Usually appears with thermometer or with a phrase naming its position, such as at the bottom of the tube. Distinguish from sense 4: this bulb is a hard glass part that holds liquid, not a soft part you press.

Common Mistakes

The number is inside the bulb.
The liquid is inside the bulb, and the number is on the scale.
In a thermometer, the bulb holds the liquid; the numbers are printed outside.

4. the soft round end on some tubes or droppers that you press to push air or liqui

4.nounC1
Definition

the soft round end on some tubes or droppers that you press to push air or liquid through.

Example

Hana squeezed the rubber bulb to fill the dropper with medicine.

collocation: squeeze the rubber bulb

A blue bulb at the tube's end sent air into the fish tank.

bulb at the end of a tube

Common collocations
  • rubber bulb
  • squeeze the bulb
  • press the bulb
  • dropper bulb
  • bulb syringe
Synonyms

Grammar Patterns

squeeze the bulb

press the bulb

bulb at the end of a tube

Usage Note

Usually modified by rubber, soft, or suction, and used with verbs like squeeze or press. Distinguish from sense 3: this part is flexible and is used by hand to move air or liquid.

Common Mistakes

Push the tube to take up the medicine.
Squeeze the bulb to draw up the medicine.
The bulb is the soft part you press; the tube is the narrow part that carries the liquid.

Word family

  • bulbous
    adjectiveC1

Synonym discussion

Sense: noun/2

For this sense, bulb names the replaceable part of an electric light, especially the piece that fits into a socket and shines. Light bulb is the full everyday phrase and is safer when the situation is not already clear. Lamp often means the whole object on a desk, wall, or ceiling, so it is not always the same as bulb. LED can mean the lighting technology or a modern bulb type that uses less power and stays cooler. Tube is used for long fluorescent lights, not the usual round household bulb. You change a bulb in a lamp, but you do not usually say change the lamp when only the shining part has failed.

bulb ↗light bulblamp ↗LEDtube ↗

Etymology

GreekLatinEnglish

Bulb came into English from Latin bulbus, a word for an onion-like rounded plant part, and Latin had taken it from Greek bolbos. English first used bulb for the underground part of certain plants and later extended it to glass lamp parts and other rounded ends because they looked similar in shape.