Leech vs. Slug — What's the Difference?

A worm with a segmented body.

A bullet or projectile.

A person who exploits others.

A piece of metal pressed into shape.

A worm used in medicine historically.

An amount of an alcoholic drink.

Leeches are segmented parasitic or predatory worms that comprise the subclass Hirudinea within the phylum Annelida. They are closely related to the oligochaetes, which include the earthworm, and like them have soft, muscular, segmented bodies that can lengthen and contract.

Slug, or land slug, is a common name for any apparently shell-less terrestrial gastropod mollusc. The word slug is also often used as part of the common name of any gastropod mollusc that has no shell, a very reduced shell, or only a small internal shell, particularly sea slugs and semislugs (this is in contrast to the common name snail, which applies to gastropods that have a coiled shell large enough that they can fully retract its soft parts into the shell).

Any of various chiefly aquatic carnivorous or bloodsucking annelid worms of the class (or subclass) Hirudinea, of which one species (Hirudo medicinalis) was formerly widely used by physicians for therapeutic bloodletting.

A round bullet larger than buckshot.

One that preys on or clings to another; a parasite.

A shot of liquor.

(Archaic) A physician.

An amount of liquid, especially liquor, that is swallowed in one gulp; a swig.

Either vertical edge of a square sail.

A small metal disk for use in a vending or gambling machine, especially one used illegally.

The after edge of a fore-and-aft sail.

A lump of metal or glass prepared for further processing.

To bleed with leeches.

A strip of type metal, less than type-high and thicker than a lead, used for spacing.

To drain the essence or exhaust the resources of.

A line of cast type in a single strip of metal.

To attach oneself to another in the manner of a leech.

A compositor's type line of identifying marks or instructions, inserted temporarily in copy.

An aquatic blood-sucking annelid of class Hirudinea, especially Hirudo medicinalis.

(Physics) The British unit of mass that accelerates at the rate of one foot per second per second when acted on by a force of one pound on the surface of the Earth.

(figuratively) A person who derives profit from others in a parasitic fashion.

Any of various terrestrial gastropod mollusks having a slow-moving slimy elongated body with no shell or with a flat rudimentary shell on or under the skin, usually found in moist habitats.

A glass tube designed for drawing blood from damaged tissue by means of a vacuum.

A sea slug.

(archaic) A physician.

The smooth soft larva of certain insects, such as the sawfly.

(Germanic paganism) A healer.

A slimy mass of aggregated amoeboid cells that develops into the spore-bearing fruiting body of a cellular slime mold.

(nautical) The vertical edge of a square sail.

(Informal) A sluggard.

(nautical) The aft edge of a triangular sail.

A hard heavy blow, as with the fist or a baseball bat.

To apply a leech medicinally, so that it sucks blood from the patient.

A commuter who slugs.

To drain (resources) without giving back.

(Printing) To add slugs to.

To treat, cure or heal.

(Informal) To drink rapidly or in large gulps

See 2d Leach.

To strike heavily, especially with the fist or a bat.

The border or edge at the side of a sail.

To wait for or obtain a ride to work by standing at a roadside hoping to be picked up by a driver who needs another passenger to use the HOV lanes of a highway.

A physician or surgeon; a professor of the art of healing.

Any of many terrestrial pulmonate gastropod mollusks, having no (or only a rudimentary) shell.

Any one of numerous genera and species of annulose worms, belonging to the order Hirudinea, or Bdelloidea, esp. those species used in medicine, as Hirudo medicinalis of Europe, and allied species.

(obsolete) A slow, lazy person; a sluggard.

A glass tube of peculiar construction, adapted for drawing blood from a scarified part by means of a vacuum.

A bullet or other projectile fired from a firearm; in modern usage, generally refers to a shotgun slug.

To treat as a surgeon; to doctor; as, to leech wounds.

A solid block or piece of roughly shaped metal.

To bleed by the use of leeches.

A counterfeit coin, especially one used to steal from vending machines.

Carnivorous or bloodsucking aquatic or terrestrial worms typically having a sucker at each end

A shot of a drink, usually alcoholic.

A follower who hangs around a host (without benefit to the host) in hope of gain or advantage

(journalism) A title, name or header, a catchline, a short phrase or title to indicate the content of a newspaper or magazine story for editing use.

Draw blood;

The imperial (English) unit of mass that accelerates by 1 foot per second squared (1 ft/s²) when a force of one pound-force (lbf) is exerted on it.

An annelid worm that sucks blood.

A discrete mass of a material that moves as a unit, usually through another material.

A creature with suckers at both ends.

A motile pseudoplasmodium formed by amoebae working together.

(railroading) An accessory to a diesel-electric locomotive, used to increase adhesive weight and allow full power to be applied at a lower speed. It has trucks with traction motors, but lacks a prime mover, being powered by electricity from the mother locomotive, and may or may not have a control cab.

(television editing) A black screen.

(metal typesetting) A piece of type metal imprinted by a linotype machine; also a black mark placed in the margin to indicate an error; also said in application to typewriters; type slug.

(regional) A stranger picked up as a passenger to enable legal use of high occupancy vehicle lanes.

A hitchhiking commuter.

(web design) The last part of a clean URL, the displayed resource name, similar to a filename.

(obsolete) A hindrance, an obstruction.

A ship that sails slowly.

To hit A hard blow, usually with the fist.

To drink quickly; to gulp; to down.

To take part in casual carpooling; to form ad hoc, informal carpools for commuting, essentially a variation of ride-share commuting and hitchhiking.

To become reduced in diameter, or changed in shape, by passing from a larger to a smaller part of the bore of the barrel.

To move slowly or sluggishly; to lie idle.

(transitive) To load with a slug or slugs.

To make sluggish.

(transitive) To hit very hard, usually with the fist.

A drone; a slow, lazy fellow; a sluggard.

A hindrance; an obstruction.

Any one of numerous species of terrestrial pulmonate mollusks belonging to Limax and several related genera, in which the shell is either small and concealed in the mantle, or altogether wanting. They are closely allied to the land snails.

Any smooth, soft larva of a sawfly or moth which creeps like a mollusk; as, the pear slug; rose slug.

A ship that sails slowly.

An irregularly shaped piece of metal, used as a missile for a gun.

A thick strip of metal less than type high, and as long as the width of a column or a page, - used in spacing out pages and to separate display lines, etc.

To move slowly; to lie idle.

To make sluggish.

To load with a slug or slugs; as, to slug a gun.

To strike heavily.

To become reduced in diameter, or changed in shape, by passing from a larger to a smaller part of the bore of the barrel; - said of a bullet when fired from a gun, pistol, or other firearm.

A projectile that is fired from a gun

An idle slothful person

Any of various terrestrial gastropods having an elongated slimy body and no external shell

Strike heavily, especially with the fist or a bat;

Be idle; exist in a changeless situation;

A gastropod without a shell.

A slow-moving person or thing.

Slugs secrete mucus that helps them move and navigate, leaving a slime trail.

Yes, both leeches and slugs are invertebrates.

Yes, leeches are sometimes used in medicine, especially in microsurgery and reconstructive surgery.

Some slugs have tiny internal shells, but they don't have the prominent external shells like snails.

A slug's tentacles are sensory organs, with some functioning as eyes.

No, not all leeches are bloodsuckers; some eat detritus or small invertebrates.

Yes, slugs are often considered pests in gardens as they can damage plants.

Yes, slugs have predators like birds, frogs, and some ground beetles.

Yes, while many leeches prefer freshwater, some can live in marine environments.

Yes, leeches can play roles in controlling certain pest populations and are also food for various predators.

While many leeches are harmless, some can attach and suck blood. It's best to handle with care.

Yes, "leech" can refer to someone exploiting others without giving back.

Yes, leeches typically have suckers and might be flatter, while earthworms are cylindrical without suckers.

Slugs can damage plants by eating their leaves, making them pests in many gardens.