Letter: Purpose

One of the main purposes of a letter is to communicate information. This could be to share news, to provide guidance or to explain something.
A letter can also aim to persuade or argue. For example, a person may write a letter to convince a company to change one of their policies or to express their viewpoint on a particular subject.
A letter can also serve to complain or demand action. This includes customer complaint letters or letters from community members to local authorities that urge for intervention.
Equally, a letter can serve to thank or appreciate. Sent after receiving a gift, service or favour, this type of letter expresses gratitude and recognises the efforts of the recipient.
Lastly, a letter can work to build or maintain relationships. Personal letters often fall into this category, where the writer simply wants to keep in touch with a friend or relative.

Identifying the Purpose in Letters

The opening sentence often signifies the purpose of a letter. A thank you letter will likely begin with expressions of gratitude, whilst a complaint will most likely start with a statement of dissatisfaction.
Aspects such as tone and formal language can offer indications. For instance, formal and polite language are common in business or academic settings whereas informal and emotive language are found in personal letters of relationship building.
The body of the letter reflects the main purpose. For instance, presenting arguments and facts indicates persuasion while stating problems and demanding solutions shows a purpose to complain.
Similarly, closing remarks can also help identify the purpose. Friendly closings indicate relationship-building, adamant or demanding endings may suggest complaint while sincere closings suggest gratitude.
One can also infer the purpose by considering the context or relationship between the sender and recipient. For instance, letters among friends or family members are typically personal and relational whereas letters to companies or institutions are often formal.