Mensch (Yiddish: מענטש mentsh, German: Mensch, for human being) means "a person of integrity and honor". The opposite of a mensch is an nmensch (meaning: an utterly cruel or evil person). According to Leo Rosten, the Yiddish maven and author of The Joys of Yiddish, mensch is "someone to admire and emulate, someone of noble character. The key to being “a real mensch” is nothing less than character, rectitude, dignity, a sense of what is right, responsible, decorous".
In Yiddish (from which the word has migrated into American English), mensch roughly means "a good person." A "mensch" is a particularly good person, like "a stand-up guy," a person with the qualities one would hope for in a dear friend or trusted colleague. Mentschlekhkeyt (Yiddish: מענטשלעכקייט, German: Menschlichkeit) are the properties which make one a mensch.
During the Age of Enlightenment in Germany, the term "Humanität" in the philosophical sense of humanity, was used for "a better human being" or Humanism. The concept goes back to Cicero's Humanitas and was literally translated into the German word Menschlichkeit and further refined into "mentsh" in Yiddish language use.
In Modern Israeli Hebrew, the phrase Ben Adam (בן אדם) is used as an exact translation of Mensch. Though it usually means simply "a person" (literally, "son of Adam") in general, it is used to mean "a nice guy" in the same way as mensch. This usage may have developed by analogy with Yiddish or by adaptation from Arabic (from which colloquial Israeli Hebrew takes much vocabulary), in which the cognate construction Bani Adam (بني آدم) has the same meaning.
Derived from the Middle High German mensche, mensch, from the Old High German mennisko (from OHG mennisk). Originally an adjective in Old High German, the word has become a noun in standard New High German, but this is not the case in all German dialects. Cognates include Swedish människa.