Newts metamorphose through three distinct developmental life stages: aquatic larva, terrestrial juvenile (eft), and adult.

Adult newts have lizard-like bodies and return to the water every year to breed, otherwise living in humid, cover-rich land habitats.

The initial "n" was added from the indefinite article "an" by provection (juncture loss) ("an eft" → "a n'eft" → ...) by the early 15th century.

[2] The form "newt" appears to have arisen as a dialectal variant of eft in Staffordshire, but entered Standard English by the Early Modern period (used by Shakespeare in Macbeth iv.1).

During their terrestrial phase, newts live in humid habitats with abundant cover such as logs, rocks, or earth holes.

[citation needed] Newts share many of the characteristics of their salamander kin, Caudata, including semipermeable glandular skin, four equal-sized limbs, and a distinct tail.

[9] The cells at the site of an injury have the ability to undifferentiate, reproduce rapidly, and differentiate again to create a new limb or organ.

After courtship rituals of varying complexity, which take place in ponds or slow-moving streams, the male newt transfers a spermatophore, which is taken up by the female.

[citation needed] During the subsequent few months, the larvae undergo metamorphosis, during which they develop legs, and the gills are absorbed and replaced by air-breathing lungs.

"[12][13] Only when the eft reaches adulthood will the North American species return to live in water, rarely venturing back onto the land.

Most newts can be safely handled, provided the toxins they produce are not ingested or allowed to come in contact with mucous membranes or breaks in the skin.

Phylogenetic analyses have however shown that species in the Salamandridae traditionally called newts do form a monophyletic group.

Pleurodeles Echinotriton Tylototriton Notophthalmus Taricha Lissotriton Neurergus Ommatotriton Calotriton Triturus Euproctus Ichthyosaura Laotriton Pachytriton Cynops Paramesotriton Phylogenetic analyses estimated the origin of the newt subfamily in the Late Cretaceous to Eocene.

[1] Several fossil salamanders have also been referred to the Pleurodelinae, including:[18] The heart of newts, like that of most amphibians, consists of two atria and one ventricle.

[21] Adult crested newts (Triturus cristus) were found to breathe mainly via the skin but also through the lungs and the buccal cavity.

[25] During hibernation, an increase in liver pigment cells allows for storage of oxygen, as well as other important ions and free radicals.

[30] Thermoregulation, in combination with seasonal acclimation, describes the major mechanisms of how newts, as ectotherms cope with the changing temperatures existing in their environments.

[34] The newt is regarded as an ideal vertebrate model for investigating the mechanism(s) controlling the transition from mitosis to meiosis during spermatogenesis.

[37] In experiments allowing Italian crested newts to be exposed to nonylphenol, an endocrine disruptor common in leakage from sewers, there was a decrease in corticosterone and aldosterone, hormones produced by the adrenal gland and important for stress response.

[39] Some newt populations in Europe have decreased because of pollution or destruction of their breeding sites and terrestrial habitats, and countries such as the UK have taken steps to halt their declines.

It is illegal to catch, possess, or handle great crested newts without a licence, or to cause them harm or death, or to disturb their habitat in any way.