noun
Only when written 世
Refers to the human world or society at large, often in expressions like 世に知られる and 世の中.
世の中には、いろいろな考え方がある。
There are many different ways of thinking in society.
彼の発明はすぐに世に知られた。
His invention soon became known to the public.
noun
Mostly found in set or literary-sounding expressions such as 世を去る, meaning to leave this life or pass away; not the usual everyday word for one's life, which is 人生 or 生活.
彼は若くして世を去った。
He passed away at a young age.
noun
age; era; period; generation
Used for a historical age or social period; the 代 spelling with reading よ is possible but much less common than 世 in ordinary learner-facing contexts.
武士の世が終わり、明治の世が始まった。
The age of the samurai ended, and the Meiji era began.
noun
Historical or elevated use for the period of someone's rule, especially in phrases like 徳川の世 or 王の世.
徳川の世が終わると、国の仕組みも大きく変わった。
When Tokugawa rule ended, the structure of the country also changed greatly.
noun
the times; the age we live in
Only when written 世
Refers rhetorically to the current state or trend of the times, as in 世はまさに....
世はまさにデジタル化の時代だ。
The times are truly an age of digitalization.
noun
world of existence
Only when written 世
Buddhist use for the world of existence, often with a nuance of the deluded or suffering world from which one seeks liberation.
仏教では、迷いの世を離れることが理想とされる。
In Buddhism, leaving the world of deluded existence is regarded as an ideal.
A more concrete and common word for the world as a place or the global world; 世 is shorter and often appears in fixed, literary, or social expressions.
Means society or people in general, often with a nuance of public opinion or social judgment; 世 is broader and can also mean an age, reign, or life.
The ordinary modern word for an era or period. 世 can mean an age or period too, but often sounds more literary, rhetorical, or fixed in expression.
よ is a native Japanese reading conventionally written with 世 for the world, society, and ages, and with 代 for age, generation, or reign. The deeper historical derivation is uncertain.