Look at the sentences below –
1. My friend John, is a good painter.
2. My friend, John is a good painter.
Sentence 1 is grammatically incorrect.
In sentence 2 it is not clear whether the speaker is referring to John as his friend, or the person he is talking to as his friend. To understand this better, let us replace My friend with a name in sentence 2 – Tina, John is a good painter.
3. My friend, John, is a good painter.
4. My friend John is a good painter.
Both these sentences are correct and convey the same thing. The rule is – either have the commas both before and after a name, or don’t add it at all. This is because the sentence is talking about a particular person John. The addition of commas gives extra emphasis to the name.
Look at the below sentence –
Here the comma is not essential because the clause beginning with who, does not identify John. Note that even without the clause ‘who is a better painter than me’, the sentence is grammatically correct and conveys the message.
While introducing someone, we use commas.
· This is Jane, my sister.
In the second sentence, the comma before and after the name indicates we are talking about a specific scientist of AKL University. The comma after the name also tells us that the information after the name is essential to identify the person.
üWhile introducing a person
üWhere the clause before/after the name is not essential.
Few more examples –
· Thankfully, Sumy could come and help me.
· This is Monica, my colleague.