An obligation is a course of action that someone is required to take, whether legal or moral. There are also obligations in other normative contexts, such as obligations of etiquette, social obligations, religious and possibly in terms of politics, where obligations are requirements which must be fulfilled. These are generally legal obligations, which can incur a penalty for non-fulfilment, although certain people are obliged to carry out certain actions for other reasons as well, whether as a tradition or for social reasons.
Obligations vary from person to person: for example, a person holding a political office will generally have far more obligations than an average adult citizen, who themselves will have more obligations than a child. Obligations are generally granted in return for an increase in an individual's rights or power. For example, obligations for health and safety in a workplace from employer to employee maybe to ensure the fire exit is not blocked or ensure that the plugs are put in firmly.
The word "obligation" can also designate a written obligation, or such things as bank notes, coins, checks, bonds, stamps, or securities.
The term obligate can also be used in a biological context, in reference to species which must occupy a certain niche or behave in a certain way in order to survive. In biology, the opposite of obligate is facultative, meaning that a species is able to behave in a certain way and may do so under certain circumstances, but that it can also survive without having to behave this way. For example, species of salamanders in the family Proteidae are obligate paedomorphs, whereas species belonging to the Ambystomatidae are facultative paedomorphs.
In the Catholic Church, Holy Days of Obligation or Holidays of Obligation, less commonly called Feasts of Precept, are the days on which, as canon 1247 of the Code of Canon Law states, the faithful are obliged to participate in the Mass.