# union /ˈjunjən/ (US) · /jˈuːniən/ (UK) Source: https://englishreference.com/word/union Updated: 2026-08-15 ## Senses ### 1. workers' organisation noun · CEFR B1 an organisation of workers that protects their rights and helps them talk to their employers. For teachers: an organised association of workers formed to protect and further their rights and interests; a trade union. - The workers decided to join the union to ask for better pay. - The union representatives met with the board of directors to negotiate a new collective bargaining agreement regarding workplace safety. ### 2. political/state alliance noun · CEFR B2 a group of states or countries that have joined together to form one political unit. For teachers: a political unit consisting of a number of states or provinces that have joined together for a common purpose. - The European Union allows people to travel easily between member countries. - The treaty aimed to create a more perfect union between the neighbouring territories, harmonising their trade laws and border controls. ### 3. joining together noun · CEFR B2 the act of joining two or more things into one, or the state of being joined. For teachers: the action of joining together or the state of being joined into a single entity. - The union of the two companies created the largest tech firm in the city. - The architect sought a perfect union of form and function, ensuring the building was as beautiful as it was practical. ### 4. marriage noun · CEFR B2 · Formal the state of being married or joined in a relationship. For teachers: the state of being joined in marriage or a similar long-term relationship. - Their union was celebrated by friends and family from both countries. - The legal union of the two heirs served to consolidate the family estates and end decades of litigation. ### 5. student association noun · CEFR B1 · British English an organisation at a university that looks after students' social lives and rights. For teachers: a student organisation at a university or college providing social facilities and representing student interests. - We went to the student union to grab a cheap lunch between lectures. - The student union voted to boycott the new campus catering contract in protest of rising prices. ### 6. mathematical set noun · CEFR C1 · Technical a set that contains all the members of two or more other sets. For teachers: the set containing all elements that are members of at least one of a given collection of sets. - The union of set A and set B includes every number found in either group. - To solve the probability problem, the students had to calculate the union of two overlapping data sets. ### 7. programming structure noun · CEFR C2 · Technical a special way to store data where different types of information share the same memory space. For teachers: a data structure that allows multiple variables to share the same memory location, though only one can be used at a time. - The programmer used a union to save memory in the embedded system. - Unlike a struct, a union allocates only enough memory for its largest member, which requires careful management of data types. ### 8. related to a labour group adjective · CEFR B2 describing something that belongs to or is done by a workers' union. For teachers: pertaining to or represented by a labour union. - He is a union member and never misses a monthly meeting. - The company faced criticism for hiring non-union contractors to complete the electrical work on the new factory. ### 9. to combine sets verb · CEFR C2 · Technical to combine two groups of things into one large group in mathematics. For teachers: to perform the union operation on two or more mathematical sets. - If you union these two lists, you get a complete list of all customers. - The algorithm was designed to union the results of several database queries into a single, deduplicated output. ## Examples - She joins the local teachers' union. - The factory workers formed a union to negotiate for higher wages and better safety standards. - The historic union of the two rival companies created a new market leader, but it also led to complex challenges in merging their distinct corporate cultures. --- 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.