filament

noun

fil·​a·​ment ˈfi-lə-mənt 

: a single thread or a thin flexible threadlike object, process, or appendage (see appendage sense 2): such as

a

: a tenuous (see tenuous sense 2) conductor (as of carbon or metal) made incandescent by the passage of an electric current

specifically : a cathode (see cathode sense 2) in the form of a metal wire in an electron tube

b(1)

: a thin and fine elongated constituent part of a gill (see gill entry 2 sense 1)

(2)

: an elongated thin series of cells attached one to another or a very long thin cylindrical single cell (as of some algae, fungi, or bacteria)

c

: the anther-bearing stalk of a stamen see flower illustration

filamentary

ˌfi-lə-ˈmen-t(ə-)rē 

adjective

filamentous

ˌfi-lə-ˈmen-təs 

adjective

Synonyms

• fiber
• wire
• thread

Examples of filament in a Sentence

algae covered with tiny filaments

the cable was made up of fine filaments twisted together

Recent Examples on the Web

Hanging below the vast cosmic heart is a knot of dust and gas known informally as the Fishhead Nebula, thanks to its vaguely oval outline and a dark dust filament that gives it the appearance of an aquatic creature. —Anthony Wood, Space.com, 19 Oct. 2025

Asian Pacific Fibers x Blocktexx Indonesian polyester filament yarn manufacturer Asian Pacific Fibers has partnered with textile recycling technology company BlockTexx to develop and supply T2T rPET products. —Alexandra Harrell, Sourcing Journal, 16 Oct. 2025

These filaments have long been observed in real clusters like Perseus but never before reproduced in a simulation. —Neetika Walter, Interesting Engineering, 1 Oct. 2025

In the moment, her words offered a filament of hope. —Ruth Marcus, New Yorker, 26 Sep. 2025

Word History

Etymology

Middle French, from Medieval Latin filamentum, from Late Latin filare to spin — more at file

First Known Use

1594, in the meaning defined above

Rhymes for filament

• monofilament

Kids Definition

filament

noun

fil·​a·​ment ˈfil-ə-mənt 

: a single thread or a thin flexible threadlike object, process, or part: as

a

: a wire (as in a light bulb) that is made to glow by the passage of an electric current

b

: a long chain of cells (as of some bacteria or algae)

c

: the anther-bearing stalk of a plant stamen

filamentous

ˌfil-ə-ˈment-əs 

adjective

Medical Definition

filament

noun

fil·​a·​ment ˈfil-ə-mənt 

: a single thread or a thin flexible threadlike object, process, or appendage

especially : an elongated thin series of cells attached one to another or a very long thin cylindrical single cell (as of some algae, fungi, or bacteria)

filamentous

ˌfil-ə-ˈment-əs 

adjective