tauto-, taut- +

1. The needless repetition of an idea; especially, in words other than those of the immediate context, without imparting additional force or clearness, as in “widow woman”.
2. The redundant repetition of a meaning in a sentence, using different words.
3. In rhetoric, a tautology is the use of redundant language in speech or writing, or, put simply, "saying the same thing twice".
4. In logic: a compound propositional form all of whose instances are true, as “A or not A”; a proposition or statement that, in itself, is logically true; as, "Today, that competing swimmer will win or will not win."

A reference to the same menstrual period.

Pertaining to the same part, especially sending processes to help in the formation of the white matter in the same side of the spinal cord; said of certain neurons and neuroblasts.

1. Chemical isomerism in which the isomeric forms differ little, usually only in the position of a hydrogen atom, and are able to exist in equilibrium and react with each other.
2. The relationship that exists between two structural isomers that are in chemical equilibrium and freely change from one form to the other.

1. A scientific name in which the same word is used for genus and species (Chloris chloris; the greenfinch). It is said that this practice is no longer approved by the International Code of Botanical Nomenclature.
2. A taxonomic designation; such as, Gorilla gorilla and Apus apus (common swift); in which the genus and species names are the same, commonly used in zoology but no longer in botany.
3. Words that are double strings: "The following words are tautonyms: beriberi, booboo, coco, mama, murmur, and papa."

A reference to a scientific name in which the generic and the specific names are the same; such as, Chloris, chloris (the greenfinch).

The state of having the species or subspecies name identical to the generic name of the genus in which it is placed.

Absolute tautonymy is the identical spelling of a generic or subgeneric name and the specific or subspecific name of one of its originally included nominal species or subspecies.

Linnaean tautonymy is the identical spelling of a new generic or subgeneric name established before 1931 and a pre-1758 name cited as a synonym of only one of the species or subspecies originally included in that genus.

Virtual tautonymy is the nearly identical spelling, or the same origin or meaning, of a generic or subgeneric name and the specific or subspecific name in a binomen or trinomen (not a term regulated by the International Code of Zoological Nomenclature).

A method of treating or eliminating the bad effects of standard drugs by using other identical medication: With the system of tautopathy, a person who suffers from one medicament can take another similar potentised one in order to remove the bad side-effects caused by the first medicament.

Repetition of the same (vocal) sound.

In poetry, the repetition of the same metrical foot; a double foot or dipody consisting of the same foot repeated twice.

Occurring within the same syllable: The (s) and (t) are tautosyllabic in the word disturb, but not in distaste.

1. The primary type of the type species of a genus established by virtue of tautonymy.
2. The type of a genus whose species-group name is identical in spelling with the genus-group name.

Tautonymy is the possession by two or more distinct plants or animals of the same generic and specific names which are prohibited by the rules of scientific nomenclature; for example to refer to an animal as a "bison" and a plant identified as a "bison weed".

The type of a genus whose species-group name is identical in spelling with the genus-group name.