K — the eleventh letter of the English alphabet

Name and pronunciation

In English the letter is named "kay". Its most common sound is the voiceless velar plosive /k/, as in "kite" and "cat." In many languages this value is preserved; in others the pronunciation shifts according to phonetic context. A notable orthographic pattern in English is the silent K before n, as in "knife", "know", and "knight" — a remnant of older pronunciations now lost in common speech.

History and form

The shape of K traces back to ancient Semitic scripts, where a character representing a hand or open palm developed into the Phoenician sign that gave rise to the Greek letter kappa. Kappa passed into the Etruscan and Latin alphabets and produced the modern uppercase K and lowercase k forms. The letter's basic structure — one vertical stroke with two diverging diagonals — has remained recognisable through these transformations.

Uses, symbols and examples

• As a unit symbol and abbreviation: lowercase k commonly denotes kilo- (thousand) in metric contexts; it is also used informally to mean one thousand in everyday contexts and digital messages.
• In science: uppercase K is the chemical symbol for potassium and the symbol for the Kelvin temperature unit.
• In computing and notation: k sometimes stands for multiples of 1024 in technical contexts, though standards bodies distinguish kilobyte (kB) from kibibyte (KiB).
• In writing and typography: the letter pairs with others in digraphs (e.g., ck in "back") and appears in many common morphemes and abbreviations.

Notable facts and distinctions

K is relatively uncommon as an initial letter in English compared with some vowels and consonants, but it plays an important role in word formation and loanwords. Its silent use (before n) reflects historical sound changes; its symbolic roles in science and measurement give it utility beyond ordinary spelling. The visual simplicity of its strokes makes it easy to recognise in printed and handwritten forms.