Iotacism is the process by which a number of vowels and diphthongs in Ancient Greek converged in pronunciation so that they all sound like iota ([i]) in Modern Greek. In the case of the letter eta specifically, this process is known as itacism (from the resulting pronunciation of the letter's name as [ˈita]).
Ancient Greek had a broader range of vowels (see Ancient Greek phonology) than Modern Greek. Eta (η) was a long open-mid front unrounded vowel /ɛː/, and upsilon (υ) was a close front rounded vowel /y/. Over the course of time, both of these vowels came to be pronounced like the close front unrounded vowel iota (ι) [iː]. In addition, certain diphthongs merged to the same pronunciation, especially epsilon-iota (ει) and (later) upsilon-iota (υι).
In Modern Greek the letters and digraphs "ι, η, υ, ει, οι, ηι, υι" are all pronounced "i", [i].
Due to iotacism, some words with originally distinct pronunciations are now pronounced similarly, and this is sometimes the cause of differences between manuscript readings in the New Testament. For example, the upsilon of ὑμεις, ὑμων humeis, humōn "you, your (pl.)" and the eta of ἡμεις, ἡμων hēmeis, hēmōn "we, our" could be easily confused if a lector were reading to copyists in a scriptorium. As an example of a relatively minor (almost insignificant) source of "variant readings", some ancient manuscripts spelled words the way they sounded, such as the 4th-century Codex Sinaiticus, which sometimes substitutes a plain iota for the epsilon-iota digraph and sometimes does the reverse.
You took a first-class trip to Paris
You danced in the streets of Spain
You followed the sun to Rio de Janeiro
Cuz you got so sick and tired of the London rain
But honey, late at night
When you close your tires eyes
You'll be there
And I'll be here
And one of us will cry
It's me, it's me
When you need something more
Something you're dying for
It's me, it's me
When you can't see too clear
Baby, I'm always near
It's me
You played your cards, you felt the sorrow
Cuz all that dealer dealt was pain
But baby, where you gonna play tomorrow
The stakes were too damn high
And now, you're broke again
You can trip around till all your
money's blown
But who's the man that'll take you in
When all your luck is gone
It's me, it's me
What are you searching for
I know you can find my door
It's me, it's me
I know you've sinned every sin
But I'll still take you in
It's me
And me I'm sitting here
Nothing much has changed
You broke my heart to pieces babe
But that's nothing strange
Well, I ain't angry
That's all come and gone
My arms are still open wide girl
To catch you when you fall
And if someday you realize
Just where you belong
I'm the man that'll take you in
When all your luck's gone
It's me, it's me
When you need something more
Something you're dying for
It's me, it's me
When you can't see too clear
Baby, I'm always near
It's me, it's me
What are you searching for
I know you can find my door
It's me, it's me
I know you've sinned every sin
But I'll still take you in
It's me