• Consonance
• Consonant Clusters
• Digraph
• Glottal Stop
• Grimm's Law
• Phonetics
• Pronunciation
• Sound Change
• Spelling
• Stops
• Syllable

Examples and Observations:

• "There are 21 consonant letters in the written alphabet (B, C, D, F, G, H, J, K, L, M, N, P, Q, R, S, T, V, W, X, Y, Z), and there are 24 consonant sounds in most English accents. . . . Because of the erratic history of English spelling, there is no neat one-to-one correlation between letters and sounds."
  (David Crystal, The Cambridge Encyclopedia of the English Language. Cambridge University Press, 2003)
• "The 24 usual consonants occur in the following words, at the beginning unless otherwise specified: pale, tale, kale, bale, dale, gale, chain, Jane, fail, thin, sale, shale, hale, vale, this, zoo; (in the middle of) measure, mail, nail; (at the end of) sing, lay, rail, wail, Yale. Not one of these consonants is spelled in a completely consistent way in English, and some of them are spelled very oddly and inconsistently indeed. Note that our alphabet has no single letters for spelling the consonants in chain, thin, shale, this, measure, and sing. Those letters that are commonly used for spelling consonants may be called consonant letters, but calling them consonants is loose and misleading."
  (R.L. Trask, Mind the Gaffe! Harper, 2006)

• "In a phonetic description, we distinguish vowels from consonants in terms of how they are articulated in the vocal tract, and the associated patterns of acoustic energy."
  (David Crystal, How Language Works. Overlook Press, 2006)
• "Our B represents probably the same sound carried by the analogous letter in Near Eastern alphabets of 30 or 40 centuries ago.
  
  "It is a consonant sound. Therefore, B is a consonant letter, the first in alphabetical sequence of our 21. If asked at a dinner party to define the word 'consonant,' someone might venture, 'Well, I know it's not a vowel . . .' and that actually is the best starting point. Whereas vowels are pronounced from the vocal cords with minimal shaping of expelled breath, consonant sounds are created through obstruction or channeling of the breath by the lips, teeth, tongue, throat, or nasal passage, variously combined. Some consonants, like B, involve the vocal cords; others don't. Some, like R or W, flow the breath in a way that steers them relatively close to being vowels."
  (David Sacks, Letter Perfect. Broadway Books, 2003)
• The Lighter Side of Consonants
  "Lost Consonants is a text and image word play series which illustrates a sentence from which a vital letter has been removed, altering its meaning. Welcome to a world where children have leaning difficulties and youth can become addicted to rugs; where firemen wear fame-resistant clothing, and footballers get camp in their legs; where dogs start baking and horses start catering, and where, after several days without water, everyone is really thirty."
  (Graham Rawle, "Lost Consonants")