The synonyms ancient and obsolete are sometimes interchangeable, but ancient applies to occurrence, existence, or use in or survival from the distant past.

// ancient accounts of dragons

Some common synonyms of obsolete are ancient, antiquated, antique, archaic, old, and venerable. While all these words mean "having come into existence or use in the more or less distant past," obsolete may apply to something regarded as no longer acceptable or useful even though it is still in existence.

// a computer that makes earlier models obsolete

In some situations, the words archaic and obsolete are roughly equivalent. However, archaic implies having the character or characteristics of a much earlier time.

// the play used archaic language to convey a sense of period