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Glite Dictionary
dorsal fin

dorsal fin

5 3.5
A fin on the back of a fish or dolphin that helps it keep balance while swimming
  • noun
  • /ˈdɔrsəl fɪn/
  • Specialized
translation icon : aleta dorsal
  • The brown trout flapped its dorsal fin and splashed back into the water.

Examples

  • The city's public pier provides an excellent vantage point from which to observe thousands of fish as they race around at low tide, their long dorsal fins bobbing up and down like bumper-car antennas.

    Academic text (2002)

  • The males are larger than the females and juveniles, with more bulbous heads and exceptionally broad dorsal fins.

    Blog text (11)

  • At the bottom of swells, its dorsal fin came out of the water.

    Academic text (1997)

  • We should be able to put a tracking dart in that dorsal fin.

    The Meg (2018)

  • Individual dolphins are identified by notches and scars on their dorsal fins.

    Academic text (2001)

  • A Ukrainian researcher simulated flow around a dorsal fin to uncover why dolphins can swim so fast.

    Academic text (2007)

  • The dolphin's dorsal fin sliced through the water as it leaped into the air.

  • I could see the dorsal fin of the whale as it swam gracefully near the surface.

  • The shark approached with its menacing dorsal fin visible above the waves.

Synonyms

fin
vsdorsal fin
45 1.0

A flat part on a fish's body that helps it swim and stay balanced

is the single unpaired appendage on the back that helps balance
dorsal
vsdorsal fin
  • Specialized
3 4.9

The back of an animal, often a fin on a fish

is the single unpaired appendage on that back providing swimming balance

Surface Forms

dorsal fin singular
dorsal fins plural

Morphology

dorsal + fin

The meaning is directly and transparently derived from combining 'dorsal' (on or relating to the back) with 'fin' (a swimming appendage), which yields the straightforward concept of a fin on an animal's back. This adjective + noun composition is standard, literal, and cross-linguistically common, so a B1 learner who knows both constituents would readily infer the MWE's meaning.

Etymology

Dorsal fin uses dorsal for 'back' and fin for the flat swimming part. Think of a shark's fin sticking up from its 'back'; that fin helps keep the animal steady, so the name means the fin that keeps balance while swimming.