हर एक ऐसा जो अज्ञात हो।

कोई आदमी आकर यह चिट्टठी दे गया था।
कोई

Not known.

An unknown amount.
An unknown island.
An unknown writer.
An unknown source.
unknown

बहुतों में से चाहे जो एक।

दर्शकों में से कोई मंच पर आ जाएँ।
कोई

One or some or every or all without specification.

Give me any peaches you don't want.
Not any milk is left.
Any child would know that.
Pick any card.
Any day now.
Cars can be rented at almost any airport.
At twilight or any other time.
Beyond any doubt.
Need any help we can get.
Give me whatever peaches you don't want.
No milk whatsoever is left.
any, whatever, whatsoever