…lasting for an unknown or unstated length of time…
…a determiner (a and an in English) that introduces a noun phrase and implies that the thing referred to is non-specific (as in she bought me a book; government is an art; he went to a public school). Typically, the indefinite article is used to introduce new concepts into a discourse…
…a pronoun that does not refer to any person, amount, or thing in particular, e.g. anything, something, anyone, everyone…
…an integral expressed without limits, and so containing an arbitrary constant…
