You must be well familiar with the verb ‘reciprocate’ which means to give back or give in return. A reciprocal pronoun as such is used when there are two or more individuals involved in the action and when the same is reciprocated.
The phrases ‘one another’ and ‘each other’ are pronominal phrases or reciprocal pronouns that express a mutual relation referring to the subject in the plural. Reciprocal pronouns are used to indicate an action carried out by two persons and so also the consequences experienced at the same time.
Reciprocal pronouns simplify the meaning of sentences especially where the same idea has to be expressed more than once in a sentence. For example the following sentence, “Paul gave Ann a diamond ring on their engagement ceremony and Ann gave Paul a diamond ring” can be written better using a reciprocal pronoun. There is no doubt that the following sentence sounds better, “Paul and Ann gave each other diamond rings on their engagement ceremony.”
Another example would make the usage clearer: “Paul and Ann hugged each other.” The reciprocal pronoun ‘each other’ used in the above sentence indicates that both Paul and Ann carrying out the action of hugging got the consequence, ‘hugs’ at the same time.
The reciprocal pronoun ‘one another’ is used when more than two persons are referred to in a given situation. For example as in the following cases, “The boys in this class generally help one another while doing the project.” “The members of the football team congratulated one another on winning the world cup.”
How are reciprocal pronouns used in sentences?
In common English usage you may come across more instances of the use of the reciprocal pronoun ‘each other’. This is because t he use of the reciprocal pronoun ‘one another’ sounds more formal.