These words refer to people taken as a group. Mankind points collectively to all people, past, present or future, as an entity about which statements can be made. The word can sometimes tend to sound high-flown or flowery, suggesting a context of formal rhetoric or solemn oratory; often the word functions as a personification that implies a unity of thought, action and sensibility that can be generalized from the contradictory and diverse actuality. Hence, the word may be used as a quasi-poetic or persuasive term rather than as a rendering of defensible or exact observation: arguing that mankind has always struggled forwards no matter what obstacles lay in its way; basing his politics on his view of mankind as insatiably greedy and intent on self-aggrandizement. The word can, of course, appear more neutrally without these liabilities: the cultures of mankind ; a multi-volumed work attempting to take in the whole history of mankind .

Humanity can have the same high-toned flavour as mankind: humanity in its age-old struggle for survival. By implication, however, the word points more exclusively to favourable qualities such as compassion, understanding and the ennobling emotions: instincts of love and self-sacrifice that have always pervaded humanity in times of crisis. Humanity , in fact, can refer collectively to this bundle of ennobling or civilizing virtues, whether it is seen in a single person or in all people: a man of unmistakable sympathy and humanity ; UNESCO’s attempt to show the common humanity expressed in all the cultures of the earth. Homo sapiens is a scientific term for mankind as the only surviving species of the genus Homo; the term would appear in biological or anthropological discussion, particularly in making distinctions between this species and other animals: the relation of Homo sapiens to the other primates. The term would sound affected in a more general context. Man can be used as a less formal or technical term in scientific discussion: studying the evolution of man . This word can also be used like the first two words, however, as a personification that includes all people of all times: man’s incessant temptation to solve his problems by using his fists instead of his brains.

Humankind , the most formal of these words, can sound even more high-flown than the first pair of words. Unlike humanity , however, it need not suggest only ennobling traits: the puerile attempts of humankind to understand the cosmos. Where mankind might be used to treat people collectively in narrative generalization, emphasizing a past-to-present progression, humankind lends itself to aphoristic statements about abiding traits, often stated in the historical present.

• Humankind listens to the wisdom of its prophets once a week, but the bulletins of its warlords once an hour.

Men is like humankind in tending to suggest a present-tense statement about the enduring qualities of people, good or bad: pointing out that men are the only animals that kill for pleasure. Unlike man , this word would seldom be used in scientific discussion; both words, of course, include women in the implied grouping, but men as a collective is more ambiguous about this, since it can also be used as a collective for all human males, as well. Men is useful in historical discussion since it avoids the suggestion of personified unity implicit in mankind , applying where mankind cannot to point out diversity or conflict among people: the first attempts of men to settle disputes through reason rather than violence.