Consonants are the letters in the English alphabet except for the vowels. There’re 21 consonants, and 24 consonant  sounds in English. Some of the consonant sounds are voiceless, while some are voiced. The sound of a consonant is generated by a complete or partial obstruction of the airstream by constricting the speech organs. When consonants are put together with vowels, they create syllables, which are the fundamental units of pronunciation.

Silent consonants: Consonant letters can be silent in some cases in English, such as the letter ‘b’ before ‘t’ (e.g., debt) and the letter ‘k’ before ‘n’ (e.g., knowledge). When a double consonant is there in a word, usually, one consonant  is sounded (e.g., ‘summer’ or ‘ball’).

Consonant blends: In cases where two or more consonant sounds are consecutively pronounced without an intervening vowel (e.g., in the word ‘dream’), the group is called a consonant cluster or a consonant blend. In a consonant blend, each individual letter’s sound can be heard.

Consonant digraphs: In consonant digraphs, two successive letters generate a single sound. Common examples of digraphs include the letters ‘p’ and ‘h’ that sound like an ‘f’ (e.g., in the word ‘phone’), and the letters ‘g’ and ‘h’ that also mimic the sound of ‘f’ (e.g., in ‘enough’).

Stop consonants: Consonants can also act as a means to bracket a vowel, stopping its sound. These are known as stop consonants (also called ‘plosives’) because the air in the vocal tract is entirely stopped at some point, generally by the teeth, lips, or tongue. Then the air is suddenly released to make the consonant sound. Examples of words that appear with stop consonants include ‘kit’ and ‘bib.’

Consonance: Generally, consonance refers to the repetition of consonant  sounds. More precisely, it’s the repetition of consonant sounds of important words or accented syllables. Poets and lyricists frequently use consonance to generate a sense of rhythm.

Generally, words that start with vowels are set off with the indefinite article ‘an,’ while words that begin with consonants are introduced by an ‘a.’ However, if the consonants at the beginning of a word generate a vowel sound, the article ‘an’ needs to be used (e.g., an honor).

There’re strings of consonants that are written like full words, such as ‘hmm.’ However, these are just sounds instead of actual words. One can also find that the majority of words in English don’t contain more than three consonants in a row.