The death of a language is great loss to humanity on scientific, personal, social, and cultural levels. While there are differences in opinion regarding whether some languages are isolates or not, making compilation of a definitive comprehensive list of the world's language isolates very difficult, there is general agreement about the majority of language isolates of the world and their total approximate number. The relationship between language endangerment and language isolates has strong implications for language classification and language history. Of the 159 language isolates, 59 are dormant or awakening - there is no known person left in the world who speaks any of the languages natively. Severely endangered is the second highest level of urgency for endangered languages. The term "endangered" can refer generally to all of the language isolates of any degree of vitality other than "safe", "dormant", or "awakening".