# key /ˈki/ (US) · /kˈiː/ (UK) Source: https://englishreference.com/word/key Updated: 2026-08-15 ## Senses ### 1. for a lock noun · CEFR A1 a small piece of metal used to open a lock or start a car. For teachers: a metal instrument specifically shaped to operate the bolt of a lock. - He reached into his pocket and realized he had left his house keys at the office. - The landlord handed over a heavy ring of keys, explaining which ones accessed the main gate and which opened the basement storage. ### 2. on a keyboard noun · CEFR A2 one of the buttons you press on a computer, phone, or piano. For teachers: any of the buttons or levers on a keyboard, typewriter, or musical instrument that are depressed to produce a character or sound. - If the screen freezes, try pressing the escape key to close the program. - The pianist's fingers flew across the ivory keys, executing the complex concerto with remarkable precision and emotional depth. ### 3. a solution or secret noun · CEFR B1 the most important thing that helps you understand or achieve something. For teachers: a crucial factor or explanation that provides a solution or means of understanding. - Hard work and a bit of luck were the keys to her success in business. - Identifying the primary motive of the suspect proved to be the key to solving the long-running investigation. ### 4. a guide or legend noun · CEFR B1 a list of symbols or answers that explains what things mean on a map or in a book. For teachers: an explanatory list of symbols used in a map, table, or chart; also a set of answers to a test. - Check the key at the bottom of the map to see what the different colors represent. - The textbook includes an answer key in the back so students can check their progress on the practice exercises. ### 5. music scale noun · CEFR B2 a set of musical notes that a piece of music is based on. For teachers: a group of notes based on a particular note and comprising a scale, serving as the harmonic foundation of a composition. - The song is written in the key of C major, so it sounds quite happy. - The singer requested a transposition because the original key was slightly outside her comfortable vocal range. ### 6. small island noun · CEFR C1 · American English a small, low island, especially in the Caribbean or near Florida. For teachers: a low-lying island or reef, often composed of coral or sand. - We spent our vacation exploring the different keys along the coast of Florida. - The archipelago consists of several uninhabited keys that serve as vital nesting grounds for local seabird populations. ### 7. very important adjective · CEFR B1 the most important or necessary part of something. For teachers: of paramount importance; fundamental or essential to a system or result. - Education is a key part of a child's development. - The CEO identified three key areas where the company needed to improve to remain competitive in the global market. ### 8. to type in verb · CEFR B2 to type information into a computer or device. For teachers: to enter data into a computer system using a keyboard. - You need to key in your password before you can access the files. - The clerk spent the entire afternoon keying in the data from the paper applications into the new digital database. Usage: Often used as the phrasal verb 'key in'. ### 9. to scratch a car verb · CEFR B2 · Informal to damage a car by scratching the paint with a key. For teachers: to vandalize the bodywork of a vehicle by scratching it with a metal key. - He was angry and decided to key his ex-girlfriend's car. - The security footage showed a hooded figure walking past the parked vehicles and deliberately keying the side panels of the luxury sedan. ## Examples - I need the key to my house. - She couldn't find her car key and was late for her appointment. - Understanding the historical context is the key to interpreting the novel's complex themes and allegorical structure. --- From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.