Condolence

Condolences (from Latin con (with) + dolere (sorrow)) are an expression of sympathy to someone who is experiencing pain arising from death, deep mental anguish, or misfortune.

The use of the word "condolences", in plural, is more common than "condolence". The reason for this habit is unclear, but it resembles our habit to send someone our 'regards', 'best wishes', greetings' (all plural), etc.

When individuals condole, or offer their condolences to a particular situation or person, they are offering active, conscious support of that person or activity. This is often expressed by saying, "Sorry." Often, the English language expression "My condolences" will be in a context, such as death of a friend's loved one, in which the one offering condolences is communicating a feeling of pity towards the unfortunate party. Expressions of condolence may also be used as sarcasm if one considers the complaining person to be exaggerating their suffering, especially when they appear to consider as tragic something that is relatively insignificant.

Condolence is not always expressed in sorrow or grievance, as it can also be used to acknowledge a fellow feeling or even a common opinion.

There are various ways of expressing condolences to the victims. Examples include donating money to the charity nominated by the person who has just died, writing in a condolences book or supporting the friends and family of the loved one by making meals and looking after them in various ways in times of need.

...
Wikipedia