must

• Verbo auxiliar que expresa necesidad, obligación o alta probabilidad.

An auxiliary verb used to express necessity, obligation, or strong probability.

1. Highly recommendedB1informal

   Something that is considered essential or extremely advisable to do, see, or experience.

   Imprescindible

   • This new restaurant is a must for anyone who loves Italian food.
   • The museum's new exhibit is an absolute must for art lovers.
   • Visiting the Grand Canyon is a must when you travel to Arizona.

   Sinónimoscompulsoryessentialimperativeindispensablemandatorynecessaryobligatoryrequiredrequisite

   Antónimosoptionalunnecessary

• Verbo modal que expresa obligación estricta, necesidad, deducción lógica o recomendación apremiante; se opone a 'tener que' (regla externa) y carece de forma de pasado (se sustituye por 'tuvo que').

Core modal auxiliary verb expressing strong obligation, necessity, logical deduction, or emphatic recommendation. Unlike 'have to', 'must' typically conveys internal obligation (speaker's authority or conviction) rather than external rules. Has no past tense form; 'had to' substitutes for past obligation. 'Must not/mustn't' expresses prohibition, while logical deduction uses 'must' for high-certainty positive conclusions and 'can't' for negative deductions. Forms a functional contrast with 'should' (weaker advice) and 'have to' (external necessity). Used consistently across all English varieties, though 'have got to' is more common in informal American English. Also prevalent in legal, regulatory, and formal instructional language.

1. Strong Obligation or Necessity (Internal)A2formal

   Expresses a compelling requirement, duty, or necessity originating from the speaker's authority, moral conviction, or personal judgment. This internal obligation contrasts with 'have to', which typically signals external rules or circumstances. 'Must' is common in instructions, rules, personal resolutions, and contexts where the speaker emphasizes urgency or importance. The negative form 'must not/mustn't' conveys prohibition, not absence of obligation (for which 'don't have to' is used).

   Obligación o necesidad interna

   • You must submit the application before the deadline to be considered.
   • I must finish this report tonight; the client expects it tomorrow morning.
   • Students must wear identification badges while on campus.
   • We must reduce our carbon emissions to mitigate climate change.
   • You must not share your password with anyone under any circumstances.

2. Logical Deduction or High-Certainty InferenceB1formal

   Used to express a conclusion that the speaker considers virtually certain based on available evidence, reasoning, or general knowledge. This epistemic use of 'must' indicates strong probability (near 100% confidence) in positive statements. For negative deductions (impossibility), English uses 'can't' or 'cannot', not 'must not'. Common in analytical, diagnostic, or explanatory contexts where the speaker infers a likely truth from observable facts.

   Deducción lógica o inferencia de alta certeza

   • You've been traveling all day; you must be exhausted.
   • The lights are off and nobody's answering — they must have left already.
   • She speaks French, Spanish, and Mandarin fluently; she must have studied languages extensively.
   • If the train departed at 9 AM and the journey takes three hours, it must be arriving now.
   • He always carries an umbrella; it must rain frequently where he lives.

3. Emphatic Recommendation or Strong AdviceB1informal

   Offers forceful suggestions, urgent recommendations, or compelling advice where the speaker strongly believes an action is beneficial or advisable. More emphatic than 'should' or 'ought to', this usage conveys personal conviction about the value or importance of the recommended action. Common in persuasive communication, expert guidance, health advice, or motivational contexts. The tone is encouraging rather than coercive, distinguishing it from obligation uses.

   Recomendación enfática o consejo firme

   • You must try the chocolate cake at that bakery — it's absolutely incredible!
   • If you visit Tokyo, you must experience a traditional onsen at least once.
   • You must read this book; it completely changed my perspective on leadership.
   • We must catch up soon — I have so much to tell you about the project!
   • You must see a doctor if these symptoms persist for more than a week.

4. Prohibition (Must Not / Mustn't)A2formal

   In negative form, expresses a strict prohibition, rule, or warning against performing an action. 'Must not' conveys that an action is forbidden, dangerous, or strongly discouraged by authority, safety requirements, or social norms. This differs from 'don't have to', which indicates absence of obligation (i.e., something is optional). Common in safety instructions, legal regulations, parental guidance, and institutional policies.

   Prohibición (must not / mustn't)

   • You must not enter the construction site without a hard hat and safety vest.
   • Passengers must not use electronic devices during takeoff and landing.
   • You mustn't disclose confidential client information to third parties.
   • Children must not swim in the pool without adult supervision.
   • Employees must not access company systems from unsecured public networks.

5. Formal or Legal RequirementC1formallegal

   Used in official documents, contracts, regulations, or formal instructions to stipulate mandatory actions, compliance standards, or procedural necessities. This deontic usage carries institutional authority and often appears in legal texts, technical specifications, academic guidelines, or policy documents. 'Must' in this context is preferred over 'shall' in modern drafting for clarity, though both convey binding obligation. The impersonal, authoritative tone makes it unsuitable for casual conversation but essential for precise regulatory language.

   Obligación legal o formal

   • All applicants must provide two forms of government-issued identification.
   • The software must comply with GDPR requirements for data protection.
   • Each laboratory sample must be labeled with date, time, and researcher ID.
   • Contractors must complete safety training before commencing work on site.
   • The manuscript must adhere to the journal's formatting guidelines for submission.

• Sustantivo con varios significados: puede denotar algo necesario u obligatorio, el zumo de uva antes o durante la fermentación, o la cualidad de oler o saber a rancio, mohoso o enmohecido.

A noun with multiple meanings: it can refer to a necessary or essential thing, grape juice before or during fermentation, or the quality of smelling or tasting old, stale, or mouldy.

1. Necessary or essential thingA2informal

   Something that is required or indispensable.

   cosa imprescindible

   • A good dictionary is a must for learning English.
   • Warm clothes are a must in this cold weather.
   • This book is a must-read for all history fans.

   Sinónimosessentialfundamentalimperativeindispensablenecessityneedprerequisiterequirementrequisite

   Antónimoschoiceextraluxuryoption

2. Grape juice before or during fermentationC1formalculinary

   The unfermented or partially fermented juice of grapes, used in winemaking.

   Mosto

   • The winemaker pressed the grapes to extract the must.
   • The must was left to ferment in oak barrels.
   • Sugar is sometimes added to the must to increase alcohol content.

3. Quality of smelling or tasting old or stale or mouldyC1formal

   A musty or stale odor or flavor, often associated with dampness or age.

   Olor o sabor a humedad

   • The old cellar had a distinct must about it.
   • The bread had a must that indicated it was no longer fresh.
   • He detected a must in the antique furniture.

   Sinónimosdampnessmoldinessmustinessstaleness