Look up de rigueur in Wiktionary, the free dictionary.

de rigueur is a French expression that literally means "of rigor" or "of strictness". In English language usage, it means, "necessary according to etiquette, protocol or fashion."^[1] Wikipedia does not have an article with this exact name. ... Wiktionary (a portmanteau of wiki and dictionary) is a multilingual, Web-based project to create a free content dictionary, available in over 150 languages. ... The English language is a West Germanic language that originates in England. ...

Something that is de rigueur is required by convention or fashion, but not by any hard rule. For example, among the upper classes during the Victorian era, dressing for dinner was de rigueur. In modern times, it is considered de rigueur among many wealthy New York City residents to own a weekend house in the Hamptons. Queen Victoria (shown here on the morning of her accession to the Throne, 20 June 1837) gave her name to the historic era The Victorian era of the United Kingdom marked the height of the British Industrial Revolution and the apex of the British Empire. ... New York, New York and NYC redirect here. ... The Hamptons, shown highlighted The Hamptons refers specifically to the towns of Southampton and East Hampton on the South Fork, Suffolk County, New York on the east end of Long Island, in Suffolk County, New York. ...

"De rigueur" is also a type of standard similar to a de facto standard, though de facto refers to a practice that is practically law. Standardization, in the context related to technologies and industries, is the process of establishing a technical standard among competing entities in a market, where this will bring benefits without hurting competition. ... De facto is a Latin expression that means in fact or in practice. It is commonly used as opposed to de jure (meaning by law) when referring to matters of law or governance or technique (such as standards), that are found in the common experience as created or developed without...

Like many other foreign language phrases used in English, it is often italicized when used in a written sentence.

A common English colloquial replacement for the phrase would be 'the done thing'.

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