obligatoryob‧lig‧a‧to‧ry /əˈblɪɡətəri $ -tɔːri/ ●○○ adjective 
Examples
It is obligatory for companies to provide details of their industrial processes.► see thesaurus at necessary2[only before noun] used humorously to describe something that is always done or included in a particular situation: She offered him the obligatory cup of tea.
ExamplesEXAMPLES FROM OTHER DICTIONARIES
Thesaurus- Evening dress is usual, but not obligatory.
- It is now obligatory for all competitors to wear face protectors.
- Military service is obligatory for all men between 18 and 27.
- Voting is obligatory for Brazilians aged 18 to 69.
- Appreciation of this reality begins with the popular, indeed obligatory, definition of work.
- Award-winning magician Oscar Mu oz also pulls the obligatory rabbit out of the hat, and even produces a bird or two.
- By the time I had done the obligatory 20-minute brushwork on Vaquero, my arms ached.
- For their part the priests declared that without such obligatory gifts they would not be able to survive.
- In front is a lush, densely landscaped yard; in back is the obligatory pool.
- The obligatory standing ovation when he first entered the game against the Golden State Warriors lasted less than a minute.
- The truth is that obligatory recycling protects markets as well as the environment.
- They sent out the obligatory memo both before and after the project.
THESAURUS► necessary
1formal something that is obligatory must be done because of a law, rule etc SYN compulsory, mandatoryit is obligatory for somebody (to do something) used to describe something that you need to have or do: · Make sure you bring the necessary documents with you.· It may be necessary for you to have a small operation.
► essential very important and necessary, especially in order to be healthy, successful etc: · Vitamins are essential for healthy growth.· The tourist industry is an essential part of the Spanish economy.
► vital extremely important and necessary, especially in order to avoid serious problems: · A vital piece of equipment on the spacecraft had stopped operating.· It is vital that the aid is sent immediately.
► compulsory if something is compulsory, you must do it because of a rule or law: · Maths and Science are compulsory subjects.· All new staff undergo a compulsory training course.
► obligatory if something is obligatory, you must do it because of a rule or law. Obligatory is more formal than compulsory: · The use of seatbelts is obligatory.· Safety regulations have made it obligatory for all competitors to wear fist protectors.
► mandatory if something is mandatory, you must do it because it is the law. Mandatory is more formal than compulsory and sounds stronger: · School attendance is mandatory.· a prisoner serving a mandatory life sentence
► requisite formal [usually before noun] the requisite things are the ones that you need to have in order to do something: · The other candidates lacked the requisite skills.· the requisite evidence needed for a successful prosecution
► compulsory if something is compulsory, you must do it because of a rule or law: · Maths and English are compulsory for all students.· Compulsory education was introduced in 1870.· Wearing a seat belt is compulsory.· It is now compulsory for anyone claiming state benefit to register with a job centre.
► obligatory [not usually before noun] if something is obligatory, you must do it because of a rule or law. Obligatory is more formal than compulsory: · It is now obligatory for all competitors to wear face protectors.· Evening dress is usual, but not obligatory.· Military service is obligatory for all men between 18 and 27.
► mandatory if something is mandatory, you must do it because it is the law. Mandatory is more formal than compulsory and sounds stronger: · Drug smuggling carries a mandatory death sentence.· In some countries, wearing helmets is mandatory for all cyclists.
Longman Language Activatorwhen a rule or law forces you to do something► must do something/have to do something · All competitors must arrive by 10:00 a.m.· All visitors have to sign in at the main reception desk.· I'm not sure what the procedure is -- you might have to make a written complaint.must/have to · I don't want to get rid of the animals, but we have to.
► be obliged to do something formal to have to do something, because of a legal or professional rule: · Doctors are obliged by law to try to keep their patients alive.· Members of parliament are obliged to declare all their financial interests.
► be required to do something formal to have to do something - used especially in written notices and official documents: · Visitors are required to register their names on arrival.· Under the law the President is required to notify Congress when US troops are likely to be involved in hostilities.· Companies are legally required to keep records of all their financial transactions.
► have an obligation to do something/be under an obligation to do something to have to do something because it is the duty of someone in your position to do it, or because you have officially agreed to do it: · Anyone who rents a house is under an obligation to keep it clean and tidy.· Having promised to cut taxes, the government now has an obligation to do so.
► compulsory something that is compulsory must be done, used, or provided because of a rule or law: · Smoke detectors are compulsory in all new buildings.· Compulsory education (=when all children have to go to school) was introduced in 1870.compulsory for: · Maths and English are compulsory for all students.it is compulsory (for somebody) to do something: · It is now compulsory for anyone claiming state benefit to register with a job centre.
► mandatory something that is mandatory must be done because of the law: · Drug smuggling carries a mandatory death sentence.mandatory for: · In some countries, wearing helmets is mandatory for all cyclists.
► obligatory something that is obligatory must be done because of a rule or law, or because it is expected that you will do it: · Evening dress is usual, but not obligatory.obligatory for: · Military service is obligatory for all men between 18 and 27.it is obligatory (for somebody) to do something: · It is now obligatory for all competitors to wear face protectors.
It is obligatory for companies to provide details of their industrial processes.► see thesaurus at necessary2[only before noun] used humorously to describe something that is always done or included in a particular situation: She offered him the obligatory cup of tea.