Light bulb or lightbulb?
light bulb is a noun meaning “An evacuated glass bulb containing a metal filament which is heated by…”; lightbulb is a noun meaning “Alternative spelling of light bulb”. Wiktionary gives them as spellings of the same word. light bulb is written as two words and lightbulb as one word; they are used differently.
What is the difference between light bulb and lightbulb?
| light bulb | lightbulb | |
|---|---|---|
| Part of speech | noun | noun |
| Meaning | An evacuated glass bulb containing a metal filament which is heated by electrical resistance to produce light An article that resembles such a bulb and converts electricity to light by any process | colloquialAn uninvited third person joining a couple's date who prevents or hinders romantic interactions |
| Example | a fluorescent light bulb | Being an extra big light bulb and eating with two cousins and their husband and fiance |
| Forms | light-bulbs | lightbulbs |
| Pronunciation | /ˈlaɪtˌbʌlb/ | /ˈlaɪtˌbʌlb/ |
| In writing | not counted (the list counts single words) | about once in every 2 million words |
Sources: light bulb and lightbulb in the English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0); written frequency: wordfreq 3.1 (a 2021 snapshot of Wikipedia, subtitles, news, books, web text and social media).
Every current meaning of light bulb and lightbulb
light bulb
- 1
An evacuated glass bulb containing a metal filament which is heated by electrical resistance to produce light
- 2
Alternative form of light bulb
- 3
An article that resembles such a bulb and converts electricity to light by any process
a fluorescent light bulb
- 4
Used in reference to the sudden arrival of a realization, an inspiration, an idea, or the like
a light-bulb moment
lightbulb
- 1
Alternative spelling of light bulb
- 2
colloquialAn uninvited third person joining a couple's date who prevents or hinders romantic interactions
Being an extra big light bulb and eating with two cousins and their husband and fiance
Source: the English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0); obsolete, archaic, dialect and rare senses left out.
Which is more common, light bulb or lightbulb?
light bulb is a phrase, which the list of single words does not count; lightbulb about once in every 2 million words.
Source: written frequency: wordfreq 3.1 (a 2021 snapshot of Wikipedia, subtitles, news, books, web text and social media).