The phrase "diamond in the rough" is usually used to describe a person who appears to be tough on the outside but inside has a good or kind heart. Sometimes the phrase is also used to describe a person who is in trouble with the law or associates with criminals, but is truly a good person inside. This phrase is an idiom, which means it is a commonly employed method of expressing a thought but is not meant in the literal sense. In regions in which it is common, it is typically used in casual speech rather than in formal speech or in writing.
When it comes to casual speech, a person may have multiple options for saying the same basic thing. For instance, when someone wants to point out that a person seems tough but truly has a good heart, he may simply state his opinion. In some cases, however, a person might choose a common but non-literal way to express this same thought. He could state, for example, that this person is a diamond in the rough. In places in which this phrase is commonly used, those who hear these words will usually have no trouble deciphering their meaning.
"Diamond in the rough" is an idiom, which means it is a common phrase that is used expressively. When people use this idiom, they do not mean that the person discussed is literally a diamond. Instead, they use the phrase as a non-literal expression of a person's worth or true nature. People may also use a range of other idioms to express themselves, and the most popular idioms often depend on the region in which a person lives. For instance, the phrase "diamond in the rough" may be common in such places as the United States and the United Kingdom but prove rare in some other countries.
Typically, idioms such as "diamond in the rough" are used in causal speech. They provide a fun or more colorful way of making a point or offering an opinion. They are often avoided in formal speech and writing, however. For instance, a person might use them when speaking casually to friends and associates or in emails and text messages. If the phrase is used in formal speech or writing, it is often used for the purpose of adding a fun or colorful element to a document or discussion.