Radical consonants are those consonants articulated with the root (base) of the tongue

Tongue

The tongue is a muscular hydrostat on the floors of the mouths of most vertebrates which manipulates food for mastication. It is the primary organ of taste , as much of the upper surface of the tongue is covered in papillae and taste buds. It is sensitive and kept moist by saliva, and is richly...

 in the throat

Throat

In vertebrate anatomy, the throat is the anterior part of the neck, in front of the vertebral column. It consists of the pharynx and larynx...

. This includes the pharyngeal

Pharyngeal consonant

A pharyngeal consonant is a type of consonant which is articulated with the root of the tongue against the pharynx.-Pharyngeal consonants in the IPA:Pharyngeal consonants in the International Phonetic Alphabet :...

, epiglottal

Epiglottal consonant

An epiglottal consonant is a consonant that is articulated with the aryepiglottic folds against the epiglottis. They are occasionally called aryepiglottal consonants.-Epiglottal consonants in the IPA:...

, and epiglotto-pharyngeal

Epiglotto-pharyngeal consonant

An epiglotto-pharyngeal consonant is a newly reported type of consonant, articulated with the epiglottis against the back wall of the pharynx. This contrasts with the pharyngeal consonants, where the root of the tongue contacts the back wall of the pharynx, and prototypical epiglottal consonants,...

 places of articulation, though technically epiglottal consonants take place in the larynx

Larynx

The larynx , commonly called the voice box, is an organ in the neck of amphibians, reptiles and mammals involved in breathing, sound production, and protecting the trachea against food aspiration. It manipulates pitch and volume...

.

The term radical was coined to help disambiguate pharyngeal, which had come to mean any consonant articulated in the throat, whether the articulator was the back of the tongue ("high" pharyngeals) or the epiglottis ("low" pharyngeals). However, the term pharyngeal is still commonly used in the broader sense, and authors such as Miller (2005) prefer guttural, which may include glottal consonant

Glottal consonant

Glottal consonants, also called laryngeal consonants, are consonants articulated with the glottis. Many phoneticians consider them, or at least the so-called fricative, to be transitional states of the glottis without a point of articulation as other consonants have; in fact, some do not consider...

s as well.