lex
Greekword, speech, diction
About This Root
The root lex comes from Greek lexis, 'a word, a way of speaking, diction,' which grew out of the verb legein, 'to speak, to say.' Where most word-roots are about doing things in the world — carrying, breaking, sending — lex is about language itself. It is a metalinguistic root: words made of lex are words for talking about words.
The clearest member is lexicon. In Greek, a lexikon (biblion) was simply a 'word-book.' English borrowed it whole, and a lexicon is still a collection of words — sometimes a literal dictionary, sometimes the entire vocabulary of a language, a field, or even a single person ('the lexicon of computing'; 'it entered the political lexicon'). Add the adjective ending and you get lexical, 'relating to words or vocabulary,' the term linguists use when they mean 'at the level of individual words' rather than grammar or sound (lexical meaning, a lexical gap).
The surprising member is dyslexia. Break it down: dys- (a Greek prefix for 'bad, difficult, impaired') + lex (word) + -ia (a condition) = literally 'difficulty with words.' It names the learning difference that makes reading and spelling hard, even for intelligent people. Here lex has quietly shifted from 'spoken word' toward 'written word,' which is where the difficulty actually shows up — proof that the root tracks language broadly, not just speech.
The pattern to take away: when you see lex inside a word, expect it to be about the words themselves — listing them (lexicon), analyzing them (lexical), or struggling to process them (dyslexia). It is language turned back on itself.
Think of a lexicon — a book of words. Every lex word is about words themselves: lexicon (a collection of words), lexical (relating to words), dyslexia (difficulty with words).
Core Words Deep Dive
The few words from this family worth telling in full — one by one.
From Greek lexikon, 'word-book.' Worth knowing because it stretches well beyond 'dictionary.' A lexicon can be (1) an actual dictionary, especially for an ancient or specialist language (a Greek lexicon); (2) the total vocabulary of a language or field (the lexicon of medicine); or (3) the words characteristic of a group or era (the word went into the everyday lexicon). The thread is always 'the stock of words available.'
lex (word) + -ical (relating to) = 'relating to words/vocabulary.' This is a technical adjective from linguistics, contrasting with grammatical or phonetic. 'Lexical meaning' is the dictionary meaning of a word itself, separate from how grammar shapes it; a 'lexical gap' is a missing word a language simply doesn't have. If you see lexical, the focus is on individual words rather than sentence structure or sound.
dys- (impaired, difficult) + lex (word) + -ia (condition) = 'difficulty with words.' The interesting twist is that the difficulty shows up mainly in reading and spelling — written words — so lex here leans toward language on the page. It is unrelated to intelligence; it is a difference in how the brain processes written symbols. Compare the sibling dysgraphia (difficulty writing) to see dys- attaching to different language skills.