A floating tone is a morpheme

Morpheme

In linguistics, a morpheme is the smallest semantically meaningful unit in a language. The field of study dedicated to morphemes is called morphology. A morpheme is not identical to a word, and the principal difference between the two is that a morpheme may or may not stand alone, whereas a word,...

 or element of a morpheme that contains no consonant

Consonant

In articulatory phonetics, a consonant is a speech sound that is articulated with complete or partial closure of the vocal tract. Examples are , pronounced with the lips; , pronounced with the front of the tongue; , pronounced with the back of the tongue; , pronounced in the throat; and ,...

s, no vowel

Vowel

In phonetics, a vowel is a sound in spoken language, such as English ah! or oh! , pronounced with an open vocal tract so that there is no build-up of air pressure at any point above the glottis. This contrasts with consonants, such as English sh! , where there is a constriction or closure at some...

s, but only tone

Tone (linguistics)

Tone is the use of pitch in language to distinguish lexical or grammatical meaning—that is, to distinguish or inflect words. All verbal languages use pitch to express emotional and other paralinguistic information, and to convey emphasis, contrast, and other such features in what is called...

. It cannot be pronounced by itself, but affects the tones of neighboring morphemes.

An example occurs in Bambara

Bambara language

Bambara, more correctly known as Bamanankan , its designation in the language itself , is a language spoken in Mali by as many as six million people...

. Bambara has two phonemic

Phoneme

In a language or dialect, a phoneme is the smallest segmental unit of sound employed to form meaningful contrasts between utterances....

 tones, high and low. In this language, the definite article

Definite Article

Definite Article is the title of British comedian Eddie Izzard's 1996 performance released on VHS. It was recorded on different nights at the Shaftesbury Theatre...

 is a floating low tone. With a noun in isolation, it is associated with the preceding vowel, turning a high tone into a falling tone: [bá] river; [bâ] the river. When it occurs between two high tones, it downstep

Downstep (phonetics)

In phonetics, downstep is a phonemic or phonetic downward shift of tone between the syllables or words of a tonal language. It is best known in the tonal languages of West Africa, but the pitch accent of Japanese is quite similar to downstep in Africa. Downstep contrasts with the much rarer upstep...

s the following tone: it's not a river (or [bá ꜜ tɛ́]) it's not the river

Also common are floating tones associated with a segment

Segment (linguistics)

In linguistics , the term segment may be defined as "any discrete unit that can be identified, either physically or auditorily, in the stream of speech."- Classifying speech units :...

al morpheme such as an affix. For example, in Okphela, an Edoid language

Edoid languages

The Edoid languages are some two-to-three dozen languages spoken in Southern Nigeria, predominantly in the former Bendel State. The Edoid group belongs to Volta–Niger branch of Niger–Congo; the name of the group derives from its most widely spoken member, Edo...

 of Nigeria, the main negative morpheme is distinguished from the present tense morpheme by tone; the present tense morpheme (á-) carries high tone, whereas the negative past morpheme (´a-) imposes a high tone on the syllable which precedes it:

• oh á-nga he is climbing
• óh a-nga he didn't climb

Floating tones derive historically from morphemes which assimilate

Assimilation (linguistics)

Assimilation is a common phonological process by which the sound of the ending of one word blends into the sound of the beginning of the following word. This occurs when the parts of the mouth and vocal cords start to form the beginning sounds of the next word before the last sound has been...

 or lenite

Lenition

In linguistics, lenition is a kind of sound change that alters consonants, making them "weaker" in some way. The word lenition itself means "softening" or "weakening" . Lenition can happen both synchronically and diachronically...

to the point where only their tone remains.