Nasal consonant

A nasal consonant is a type of consonant produced with a lowered velum in the mouth, allowing air to come out through the nose, while the air is not allowed to pass through the mouth because something (like the tongue or the lips) is stopping it. Examples of nasal consonants in English are and , in words such as "nose" and "mouth".
Definition.
Nearly all nasal consonants are nasal stops (or nasal continuants), where air comes out through the nose but not through the mouth, as it is blocked by the lips or tongue. 
Most nasals are voiced, and, in fact, the nasal sounds and are among the most common sounds used in languages of the world. Voiceless nasals are used in a few languages, such as Burmese and Welsh. 
In terms of acoustics, nasal stops are sonorants, meaning that they do not significantly stop the flow of air (as it can come out the nose). However, nasals are also stops in their articulation because the flow of air through the mouth is blocked completely. So nasal consonants sound both like sonorants and like obstruents.
Acoustically, nasal stops have bands of energy at around 200 and 2,000 Hz.
Examples of languages containing nasal consonants:
The voiced retroflex nasal is [ɳ] is a common sound in Indic languages.
The voiced palatal nasal [ɲ] is a common sound in European languages, such as: Spanish "ñ"; or French and Italian "gn"; or Catalan, Hungarian and Luganda "ny"; or Czech and Slovak "ň"; or Polish "ń"; or Occitan and Portuguese "nh"; or Serbian, Croatian, Bosnian and Montenegrin "nj".
English, German and Cantonese have , and . Tamil has its own different letters for the sounds , , , , and (ம,ந,ன,ண,ஞ,ங).
Catalan, Occitan, Spanish, and Italian have , , as phonemes, and and as allophones. (In several American dialects of Spanish, there is no palatal nasal but only a palatalized nasal, , as in English "canyon". In Brazilian Portuguese nh is frequently pronounced as a nasalized [ j ], that is, as a nasal glide. This vowel also exists in Guaraní.)
The term 'nasal stop' will often be abbreviated to just "nasal". However, there are also nasal fricatives, nasal flaps, nasal glides, and nasal vowels, as in French, Portuguese, Catalan (dialectal feature), Yoruba, Gbe, Polish, and Ljubljana Slovene. In the , nasal vowels are indicated by placing a tilde (~) over the vowel. : French "sang" .
A few languages use voiceless nasal consonants. Some of these are Icelandic, Burmese, Jalapa Mazatec, Kildin Sami, Welsh, and Central Alaskan Yup'ik.